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Temp and Fuel Gauge don't work

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Category: The Garage
Forum Name: Electrical - non engine
Forum Description: Charging systems, lights, non-ignition system, it goes here.
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Printed Date: Mar/28/2024 at 4:49am
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Topic: Temp and Fuel Gauge don't work
Posted By: amcenthusiast
Subject: Temp and Fuel Gauge don't work
Date Posted: Oct/30/2013 at 6:41am
All the time I see AMCs for sale on EBay & it'll say the fuel gauge doesn't work and it must be one of the most embarrassing things in the world to be seen walking with a gas can 'cause you ran outta gas! The temp and fuel gauges weren't working on my rebuilt-from-a-junkyard Gremlin. I'd been checking the connections and testing the sending units with my cheap voltmeter set on ohms for continuity and all seemed ok, but still no gauges. I kept re-reading my AMC technical service manual to educate myself on the gauge circuits to get them operational. The TSM says 'the constant voltage regulator is located inside the temp gauge and supplies a regulated 5 volts to the temp and fuel gauges... if the CVR is bad, neither the temp or the fuel gauge will work & the temp gauge must be replaced...' WELL, humpf! This morning I decided I'd get up real early and go for it -to take the temp gauge apart & see what the heck they're talking about. Sure enough after carefully removing the crimped on temp gauge facia there's a bi-metallic spring inside with a set of contact points. I cleaned the contact points with a knife (super careful), reassembled for testing and -now- I've got my gauges back working again! This fix applies to Gremlin/Hornet and probably Spirit/Concord. Jav/AMX, Rebel/Matador/Ambos have external removable pronged CVRs, probably having a similar spring & contact set inside... Of course, always test the circuits first for voltage and ground continuity. Hope this helps somebody else get their gauges working again.



Replies:
Posted By: rocklandrambler
Date Posted: Oct/30/2013 at 8:12am
Good Job I think most would just go and buy a new temp gauge. I have a few of the external VR's in the garage. Think I'll try to open one up and see what I can see.

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Past AMC's
1974 Hornet X (new)
1975 Gremlin X (new)
1964 Classic 660 Cross Country
1965 American 440-H


Posted By: 401MATCOUPE
Date Posted: Oct/30/2013 at 9:20am
I am not aware of all models, but all 2 hole gauge set ups (Javelin/AMX/Rebel Ambo, etc) have external CVR.  Great troubleshooting, fuel gauge systems are not that hard to troubleshoot.  I should also be rembered on 1970 and 1971 cars with low fuel warning system the CVR is re-routed to the Low Fuel Warning relay...very common to find dead CVR internal to relay.

-------------
Ross K. Peterson
68X,GoPac,343,AT,52A(1stCar)
68X,GoPac,390,4sp,52A
69X,GoPac,390,4sp,64A
70X,GoPac,390,4sp,87A,8
70X,GoPac,390,4sp,BBO,8
70 Jav SST,390,AT,BSO
74MatX,401,AT,Prototype
74MatX,401,AT


Posted By: 304-dude
Date Posted: Oct/31/2013 at 8:19am
I did not know CVRs go bad often as they are a sealed unit... I have an extra one myself as a backup for later on down the road. Will test both, and hopefully one will be bad. If so, I can modify the thing to be a connector for a 5v regulated power to my instrument panel. Hate to do that to a good CVR, but this thread got me to thinking.


Posted By: billd
Date Posted: Oct/31/2013 at 12:07pm
They can and do go bad or get flaky - They are an electro-mechanical device with CONTACTS or points and a heating element. As such, the points can either stick (pegging the gauges) or get dirty (low or no readings - no gauge deflection), and the winding that heats the bi-metal strip can fail just like the winding or heating element in any device, be it a heating pad or hot plate.
They don't strictly actually "regulate" anything, they pulse the supply so that it averages to the voltage required for the gauges and keep it constant, otherwise the gauges would read high when the car was on a long highway trip or the voltage regulator under the hood was calling for 14 volts instead of 13, etc.
They take the variables out of the equation. More voltage in the car's system, the faster that coil heats the bi-metal strip breaking contact inside, lower voltage, like a bad charging system, the coil takes longer to heat the strip upping the average a bit.
The OP found the contacts "dirty" so nothing was going through - not even the heating coil, so the thing never passed any current at all, and never heated at all (or not enough)
So in a sense it's a whole lot like the old mechanical voltage regulators used with generators or early alternators on most cars but they control the voltage by controlling the input to the field, so the output really IS the regulated voltage, they do more of a direct control, not regulating so much.
They go bad quite a bit, more than you'd think - however, bad doesn't always mean open circuit. The metals can age causing the thing to cycle too fast or too slow leading to gauge readings that are off, like with my car, and so on.
I've experienced the same thing on Ford as well as AMC, so it's not a unique to AMC thing.
There are 3 connections required - ground, "12v" supply and output to gauges. Current goes in, through the heating coil or winding and in parallel to the gauges, then to ground. The part that goes through the winding heats the strip causing the bi-metal to bend and open the contacts. This breaks the circuit so the coil loses power, and the gauges get nothing either. The strip cools, the contacts make contact, and it starts over.
An analog volt meter will show the "average" output - it's not a true voltage reading!
You can't say that they "put out 5 volts" or "they put out 10 volts" as that simply is not true. When the contacts are closed full voltage gets trough (less the normal voltage drop across connections, etc.) The voltage out is a DIRECT connect to the voltage in when the strip is cool and relaxed.
Because the gauges themselves work on heating a coil to move the needle, they do not respond quickly to high or low voltage - but give more of an average of the duty cycle. The cycle happens so fast the gauges can't respond so you don't see the needle quiver. It's a "dampened effect". Because of this, the circuit doesn't even need any filters or capacitors to even out and smooth the output.
Anyway it's such a bloody simple circuit, albeit very delicate inside, yet one of the lesser understood areas.
By the way, it's a great reason to disconnect the battery when working on the dash and being careful to not subject the dash or gauges to bumps and sudden movements.
"amcenthusiast" has seen why first-hand. Pretty small stuff in there, right?  Wink

Guys you made me feel really old again as I'm not supposed to be able to remember all that old-skool stuff and the details. Those went away many years ago and as such it's been a very long time since I've had them open or done anything with 'em.
Gauges after those years worked more like a "regular volt meter", measuring the "voltage" using a coil inside a magnetic field - more voltage, more field from the coil, more needle deflection.


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http://theamcpages.com" rel="nofollow - http://theamcpages.com

http://antique-engines.com" rel="nofollow - http://antique-engines.com


Posted By: W1ngzThinBlueLine
Date Posted: Nov/05/2013 at 4:24pm
Do you mind posting a picture? I'm trying to diagnose mine and I'm electrically illiterate. Thanks.

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"To sin by silence when they should protest makes cowards of men."
- Abraham Lincoln


Posted By: RebelYell
Date Posted: Nov/07/2013 at 6:54pm
I am having this problem on the Barcelona I just purchased. This car also has a factory clock that doesn't work so I was wondering if it might be supplied from the CVR?  I spent time today replacing a completely melted away ignition control module, and cleaning up all the mess it made. I ran the car after it got dark and when I turned on the lights I had a little bit of a fluctuation in the intensity of the lights, especially the interior lights. I noticed it looked like voltage regulator on the fender well is brand new. The alternator is supposed to be relatively new even though it doesn't look like it. Could the voltage fluctuation be caused by a bad CVR?  

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http://s956.photobucket.com/user/dsheffie/media/DSCI05402_zps4c434594.jpg.html" rel="nofollow">


Posted By: rocklandrambler
Date Posted: Nov/08/2013 at 2:10am
Offhand I would say NO. The CVR is used only for the temp/fuel gauges. If you look in your TSM and trace out along the printed circuit board it should only affect those two items. Clocks are clocks, none of them work after a few years.

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Past AMC's
1974 Hornet X (new)
1975 Gremlin X (new)
1964 Classic 660 Cross Country
1965 American 440-H


Posted By: 401MATCOUPE
Date Posted: Nov/08/2013 at 4:11am
Rebel Yell,  Your Mat Coupe clock uses straight 12 volts, the CVR (Constant Voltage Regulator), function is to keep the fuel and temp gauges at a known constant while the "system" voltage fluctuates from a low right after start  (less then 12 volts) to a high that could be over 14 volts.  Improves accuracy of indicators.  I have only seen one Mat Coupe clock that worked, I sent the one from the "Prototype"Matador to Instrument Services, they do excellent work, they can convert to Quartz too.

-------------
Ross K. Peterson
68X,GoPac,343,AT,52A(1stCar)
68X,GoPac,390,4sp,52A
69X,GoPac,390,4sp,64A
70X,GoPac,390,4sp,87A,8
70X,GoPac,390,4sp,BBO,8
70 Jav SST,390,AT,BSO
74MatX,401,AT,Prototype
74MatX,401,AT


Posted By: sidewinder
Date Posted: Nov/08/2013 at 8:43am
This might help on the clock issue...

http://www.oldcarsweekly.com/restoration/restoration-tips/putting_the_ticktock_back_in_your_old_car_clock" rel="nofollow - http://www.oldcarsweekly.com/restoration/restoration-tips/putting_the_ticktock_back_in_your_old_car_clock

Chuck Page


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Chuck Page ,AKA Sidewinder
1968 "BLACK CHERRY" Javelin
Previous owner of 2013 Heritage Cup winner 1970 BBO AMX




Posted By: farna
Date Posted: Nov/08/2013 at 12:10pm
And this will help on the gauges not working issue:
http://www.wps.com/AMC/dashreg/index.html" rel="nofollow - http://www.wps.com/AMC/dashreg/index.html

A 63 Classic is shown, but this applies to any car with an external regulator. A Gremlin/etc. with the regulator built into the temp gauge can be fixed this way too, but you must take the gauge apart and solder wires to it to come out to the regulator. A bit more work, but if the points are bad or get corroded again after cleaning (as described above) this is a permanent fix. Well, more permanent -- the regulator can go bad or wires come loose. The regulator has to be grounded, but the gauges don't draw enough current to worry about mounting it on a heat sink. I've been running a similar setup since 1999 with no problems at all.


-------------
Frank Swygert


Posted By: 401MATCOUPE
Date Posted: Nov/08/2013 at 2:58pm
Be aware, AMC used General Time for the Matador Coupe and 4 door and Ambassador after 1974.  The link Chuck posted is for Borg Clock.  The General Time movement is not the same that is why I sent back to Instrument Services....they also sell the kits for Borg, which are fairly easy to repair/convert...I didn't ant to touch the General Time unit...the adjuster was broken in mine too.  The repaired everything including made the lens like new...great value for the $$$.

-------------
Ross K. Peterson
68X,GoPac,343,AT,52A(1stCar)
68X,GoPac,390,4sp,52A
69X,GoPac,390,4sp,64A
70X,GoPac,390,4sp,87A,8
70X,GoPac,390,4sp,BBO,8
70 Jav SST,390,AT,BSO
74MatX,401,AT,Prototype
74MatX,401,AT


Posted By: amcenthusiast
Date Posted: Nov/09/2013 at 6:59am
Thanks for your excellent explanation BUILD. Yeah, there are two electrically heated springs inside the Grem/Hornet type temperature gauge. As I understand it... the input voltage from the (yellow wire to instrument cluster printed circuit panel) ignition circuit supplies power to the first spring which has the contact points -they open and close, the spring-w-heating element calibrated to pulse around 5 volts, which then supplies the reduced voltage to the second electrically heated spring -that second one is the one that gets it's variable resistance ground from the sending unit (coolant temp send unit).

Yes; cleaning the contact points inside the temp gauge allowed voltage to 'wake up' my fuel gauge (as the temp 'CVR' supplies power to both the temp and fuel 'resistance readers'/gauges) but to my disappointment while both gauges began to operate, they both read to high because the 'CVR' spring is non-operational (it doesn't heat up and intermittently interrupt/open and close the points). So while I got them to work, they don't work correctly.

I'll be checking out FARNA's advice; to solder in some type of resistor to replace the burnt out factory 'CVR' (yeah, not really a true voltage regulator?)

I'm also interested to search for a replacement temp gauge unit that will simply swap into the factory instrument cluster. So far I've found an inexpensive Stewart Warner temp gauge that appears to have the same three stud mounting pattern but I don't know if it has the voltage reducer spring-w-contact points inside... yet

As for the Rebel/Matador/Ambo (and Jav/AMXs) temp and fuel gauges, they all have an external three prong 'CVR' that plugs into the instrument cluster printed circuit panel -it looks like a 1 1/4" x 1/2" silver metal box. -if you don't have a temp or fuel gauge, and you've already checked the sending units with an ohmmeter, that's what to check next? -see if it completes a circuit by touching those prongs with an ohmmeter...

The AMC clocks don't get voltage to operate from the reduced voltage dedicated circuit that powers the gauges -they get fused power directly from the fuse panel -either the fuse is blown, bad fuse connections, clock red wire is not plugged onto the fuse panel or the clock itself is failed? -usually a toasted/burnt/shorted winding inside the clock instrument itself?

I bet BUILD knows and can tell us how to wire or solder in a resistor, to bypass a failed factory 'CVR'... what type of resistor? where to buy?

Thanks all for patience and space on AMC Forum     


Posted By: slownugly
Date Posted: Nov/18/2013 at 6:24am


I'm in the process of converting my 68 American to solid state. I'm not sure if the original works as i got the car after sitting many years, but I want longevity, accuracy, and reliability. The American has the regulator in the fuel gauge as pictured above. Gremlin and hornet are in the water temp gauge. Because American fuel gauges are hard to find I ordered an nos gremlin/hornet gauge for 30 shipped. They have the simple 2 bolt setup and I will be adding the external regulator.

Basically, as I understand it, the purple wire coming in from the right stud is the 12 v. (I)The wire at the end of the coil is attached to the body of the gauge which is grounded ( see next paragraph for pic of how they ground the gauge) like bill described the contact points regulate the voltage out to an average and the 5 volt average goes to that top post. That post goes directly to the other gauge/s to supply the 5 volts. It's also soldered to the fuel gauge windings on the left on the inside as you can see. Then the 3rd and final post on the left is the signal (ground) coming from the fuel level sensor.

The gauge is grounded in a way that should be noted as I can see this type of thing affecting gauge performance if someone is running an original setup.




In the back of the gauge there is a plate in the center. The other gauges without a regulator do not have that because that is the ground for the gauge body and ultimately the regulator. In the second picture you can see the 3 holes. Before I painted it there was a bare spot there for the ground to make contact with the metal background. I do not need this ground as I am grounding the external regulator through ground screws in the circuit.

If you guys are interested I can post the rest of my results after I have this job completed. I'm going to bench test it all to make sure it's good. Heck I'll even use a fuel sensor to check the gauge.


-------------
28 model a                  73 gremlin drag car

74 gremlin project

00focus v8 5speed

hot rod rollback
68 american mpg project


Posted By: farna
Date Posted: Nov/18/2013 at 11:09am
Richard, that is a three prong solid state voltage regulator, not a resistor. The CVR in the temp gauge is technically an "averaging voltage regulator", though it does in fact reduce voltage, it still maintains an average of 5V. The solid state regulator will deliver a steady 5V. The gauges don't care, they will tolerate a full 12V without damage, but of course won't work correctly (as will the sending units) as the variable resistance will be way off.

A voltage reducer won't work because the charging system isn't a steady 12V. With the alternator or generator running voltage will fluctuate from 12V to 13.5V, and may drop below 12V depending on battery and charging system condition (and can go over 14V). So if you used a 7V reducer to get 5V from the 12V system it would be off a good bit at any given time. A regulator maintains a specific voltage regardless of input, though input must be higher than output for it to work. The old averaging CVR needs at least 10V to work correctly IIRC, but the little 7805 solid stat regulator only needs about 7V to work, but will tolerate something like 18V... IIRC. It will take anything a normally functioning alternator will dish out.


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Frank Swygert


Posted By: AMC1320
Date Posted: Nov/18/2013 at 6:20pm
With the help of this forum I was able to diagnose each portion of the guage system with a meter, either looking for voltage or continuity , took some trouble shooting but ended up being the radio noise suppressor that was not passing voltage thru the fuel guage. Once I jumpered it it allowed voltage to get back to the sending unit and the fuel guage works perfectly now.

It was q process of ruling out each individual component until I found the culprit.

Don't know why the noise suppressor failed, it's just a coil of fine wire, but it would not pass voltage thru it although visually it looked fine

This was on a 69 Ambassador btw

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Rob C
69 Ambassador SST HT
81 Spirit
84 Eagle Limited (Daily Driver)
82 SX4
06 Commander


Posted By: rocklandrambler
Date Posted: Nov/19/2013 at 2:09am
I'm wondering if the suppressor actually failed or just by removing it you cleaned the connecting pins allowing your jumper to have a clean connection. That suppressor probably had been touched since it was installed about 44 years ago and some corrosion might have built up between the pins and the suppressor. But, you got the gauges working again which was the task you wanted to accomplish.

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Past AMC's
1974 Hornet X (new)
1975 Gremlin X (new)
1964 Classic 660 Cross Country
1965 American 440-H


Posted By: myther
Date Posted: Nov/19/2013 at 2:28am
Glad to see you got your trouble shooted.  I was having very similar problems but had a different solution.  Always like to see how other people fix their problems.

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'68 Rambler American 2dr post
'67 Rebel Hardtop


Posted By: farna
Date Posted: Nov/19/2013 at 10:25am
Now you need to check the radio! If you use a modern FM radio you may not have a problem without the suppressor. If you still use the old original radio (AM or AM/FM) you might. You can get radio frequency interference (RFI) suppressors that go onthe alternator output. If you've upgraded to a GM style alternator it may not even be needed.


-------------
Frank Swygert


Posted By: RebelYell
Date Posted: Nov/22/2013 at 5:30pm
Took the instrument panel out of the 77 Barcelona today and swapped out the CVR with a new one and the fuel and temp gauge still did not work. I needed to replace a couple burned out bulbs so at least I got something accomplished. Back to checking more wire circuits. I've not yet got a service manual for it but I wonder if the service manual for my 74 Matador would help me out on the wiring diagrams for the 77. Anyone know if there is any difference?

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http://s956.photobucket.com/user/dsheffie/media/DSCI05402_zps4c434594.jpg.html" rel="nofollow">


Posted By: 401MATCOUPE
Date Posted: Nov/22/2013 at 6:53pm
Originally posted by RebelYell RebelYell wrote:

Took the instrument panel out of the 77 Barcelona today and swapped out the CVR with a new one and the fuel and temp gauge still did not work. I needed to replace a couple burned out bulbs so at least I got something accomplished. Back to checking more wire circuits. I've not yet got a service manual for it but I wonder if the service manual for my 74 Matador would help me out on the wiring diagrams for the 77. Anyone know if there is any difference?

Your 74 TSM will be close enough for the Fuel/Temp circuits.....the instrument clusters are basically the same....speedo head is different, but that does affect the rest.  Look for an open on the PC strip...I have tons of cluster parts for these.  If both are not working they do carry a common ground to the case...try tighten the nuts and screw on all the cluster.


-------------
Ross K. Peterson
68X,GoPac,343,AT,52A(1stCar)
68X,GoPac,390,4sp,52A
69X,GoPac,390,4sp,64A
70X,GoPac,390,4sp,87A,8
70X,GoPac,390,4sp,BBO,8
70 Jav SST,390,AT,BSO
74MatX,401,AT,Prototype
74MatX,401,AT


Posted By: RebelYell
Date Posted: Nov/25/2013 at 7:20pm
Thank you Ross, I already had put the dash back together before I got your post. Everything appeared to be in very good condition on the cluster panel but I did not check any nuts and screws. I'll continue to check in to it more when I have more time.    

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http://s956.photobucket.com/user/dsheffie/media/DSCI05402_zps4c434594.jpg.html" rel="nofollow">


Posted By: amcenthusiast
Date Posted: Nov/29/2013 at 12:49am
Hey all, found this website; http://www.earlycuda.org/tech/gauge-convert.htm

-has the bimetal 'regulator' in the fuel gauge instead of the temp (just put the parts on which ever one with the voltage controller -the one that has the three posts)

Went to Radio Shack and they had the parts; p# 276-1770 #7805 +5VDC voltage regulator 1amp & p# 272-1025 10uf electrolytic capacitor.

Found other websites doing similar things, such as getting an antique cars 6v gauges to work to complete a 12v conversion...

I made my ground/regulator attachment at the ground screw of the printed circuit panel, sitting on top of a fabricated heat sink made from thin scrap sheet aluminum; kinda' looks like a 2" x 3" fluted elephant ear. 'the ear' hangs off the back of the instrument cluster almost perpendicular, just above the fuel gauge so I put short sections of cut vacuum line on the two fuel gauge posts so it won't short out in case it gets bent down... (sorry no pic)

Before, after I cleaned the contact points inside the temp gauge, the temp gauge would peg H and the fuel gauge would soar higher than the known gas level so I'd leave the temp sending unit wire off in the engine compartment. Now after putting on the DIY kit, my gauges work to indicate approximate values. I'm still trying to tune them to get the needles more accurate.

Because it's a Gremlin in non-AMC environments, I know I must try harder to make my car the best I can- keep trying -all the little stuff adds up

I think the person with the Matador (really like those two cars pictured) should check their temp sending unit- check it for continuity to see if it makes a ground... momentarily touch the temp wire (purple?) in the engine compartment to ground and turn the key on, if the gauges come on and the temp gauge pegs H, replace the sending unit. test the fuel gauge send unit wire the same way (green?) but must crawl under car, top front of gas tank... since you've already replaced it's CVR you should be trouble free for another ten/fifteen years?

I'm curious to know what other 'solid state' things the Rambler American car might be getting

I read an Internet article on how to wire in a USB? or MP3 cable to the stock radio but I don't understand it... yet!


Posted By: slownugly
Date Posted: Nov/29/2013 at 5:49am


eBay regulator in 68 american

-------------
28 model a                  73 gremlin drag car

74 gremlin project

00focus v8 5speed

hot rod rollback
68 american mpg project


Posted By: amcabbott
Date Posted: Nov/29/2013 at 7:47am
found same issue on my bricklin sv-1




Posted By: hoosieramc
Date Posted: Apr/10/2014 at 7:40pm
I would like to know more about the E-bay regulator in an American. None of my gas gauges have a functioning regulator.

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Posted By: TexasJavelin
Date Posted: Apr/10/2014 at 7:47pm
Thanks for this info. This has happened to me 3 times and one walking trip to the gas station


Posted By: farna
Date Posted: Apr/11/2014 at 4:40pm
http://worldpowersystems.com/AMC/dashreg/index.html

That's all that "E-bay regulator" is, packaged in an aluminum heat sink enclosure, from the looks of it. TomJ and I have both been running the bare regulator for YEARS -- mine was installed in 1999 -- with no issues. If you need fancy packaging the E-bay regulator is the way to go, but you can still go into Radio Shack and by a three leg 5V regulator. One number is 7805, IIRC...


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Frank Swygert


Posted By: hoosieramc
Date Posted: Apr/14/2014 at 3:52pm
Do you have to eliminate the factory 12 volt feed to the gauges on the 67-69 American for this to work? 

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Posted By: farna
Date Posted: Apr/15/2014 at 6:58pm
No, the 12V feed goes to the regulator, the regulator output then feed the gauges.

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Frank Swygert


Posted By: gwryder
Date Posted: Apr/16/2014 at 6:15pm
Originally posted by AMC1320 AMC1320 wrote:

Don't know why the noise suppressor failed, it's just a coil of fine wire, but it would not pass voltage thru it although visually it looked fine

This was on a 69 Ambassador btw


Pretty interesting topic. I will add that the coil is an inductor, which DC voltage see's as 0 ohms. A noise spike sees it as high resistance. So considering voltage drop, the spike voltage gets dropped across the inductor because of it's apparent high resistance and the DC passes though uninterrupted. It sounds like the inductor opened up.

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John
70 AMX





Posted By: tony matthews
Date Posted: Feb/24/2016 at 3:23pm
Originally posted by RebelYell RebelYell wrote:

Took the instrument panel out of the 77 Barcelona today and swapped out the CVR with a new one and the fuel and temp gauge still did not work. I needed to replace a couple burned out bulbs so at least I got something accomplished. Back to checking more wire circuits. I've not yet got a service manual for it but I wonder if the service manual for my 74 Matador would help me out on the wiring diagrams for the 77. Anyone know if there is any difference?
Hi Im in England and i also have a barcelona 360 1978 and guess what My temp works but fuel dose not Im also checking my manuals but its so time taking and well hard....https://www.facebook.com/matthews.3591/videos/10153946669611565/


Posted By: tony matthews
Date Posted: Feb/24/2016 at 3:45pm
Hi Iv taken my fuel gauge out of my 78 barcelona ,
I noticed a tin oblong looking thing in the middle of the back of the fuel gauge,IT HAS THREE LUGS,ONE IS STAMPED IGNITION THE OTHER TWO HAVE NOTHING STAMPED ON THEM.i KNOW THAT ONE OF THE TWO LUGS NOT THE ONE STAMPED IGNITION GO TO THE GREEN WIRE WHICH I KNOW GOES TO THE SENDER UNIT IN THE TANK,I'M NOT SURE AT THIS TIME WHERE THE THIRD LUG GOES TO OR WHAT COLOUR WIRE IT CONNECTS TO BUT ILL CHECK AGAIN . SO IF I'M RIGHT THE IGNITION SUPPLIES POWER AND THE GREEN WIRE LUG TAKES IT TO OR REGISTERS OHMS RESISTANCE THE THIRD GOD KNOWS... HELP... PLEASE AND TREAT ME KINDLY THANK YOUhttps://www.facebook.com/matthews.3591/videos/10153946669611565/



Posted By: tony matthews
Date Posted: Feb/24/2016 at 3:51pm
Originally posted by tony matthews tony matthews wrote:

Hi Iv taken my fuel gauge out of my 78 barcelona ,
I noticed a tin oblong looking thing in the middle of the back of the fuel gauge,IT HAS THREE LUGS,ONE IS STAMPED IGNITION THE OTHER TWO HAVE NOTHING STAMPED ON THEM.i KNOW THAT ONE OF THE TWO LUGS NOT THE ONE STAMPED IGNITION GO TO THE GREEN WIRE WHICH I KNOW GOES TO THE SENDER UNIT IN THE TANK,I'M NOT SURE AT THIS TIME WHERE THE THIRD LUG GOES TO OR WHAT COLOUR WIRE IT CONNECTS TO BUT ILL CHECK AGAIN . SO IF I'M RIGHT THE IGNITION SUPPLIES POWER AND THE GREEN WIRE LUG TAKES IT TO OR REGISTERS OHMS RESISTANCE THE THIRD GOD KNOWS... HELP... PLEASE AND TREAT ME KINDLY THANK YOUhttps://www.facebook.com/matthews.3591/videos/10153946669611565/

BY THE WAY THE TEMPERATURE SIDE OF THE FUEL/ TEMP GAUGE WORKS JUST THE FUEL SIDE NOT WORKING THE NEEDLE WILL MOVE AS IV SHORTED IT AND IT ROSE UP AND FELL WHEN SHORT WAS REMOVED I CANT BE BOTHERED TO FIGHT WITH THE TANK SO IT WILL STAY WHERE IT IS FOR THE TIME BEING IV CHECKED THE EARTH TO THE BODY FROM THE SENDER UNIT ,IV NOTICED NO POWER THROUGH THE GREEN WIRE RUNNING TO THE SENDER FROM THE BACK OF THE FUEL GAUGE.WHAT WOULD I EXPECT TO GET WITH A METER WHEN I PROBE EARTH TO THE GREEN WIRE GOING TO THE SENDER UNIT  ANYTHING NUFFIN WHAT VOLTAGE OR OHMS... HELP


Posted By: rocklandrambler
Date Posted: Feb/24/2016 at 4:00pm
There is NO voltage on the wire that attaches to the sending unit on the tank.  Your test has proven that the gauge in the cluster is good.  You need to make sure the sending unit is grounded (earthed) with a separate wire from the body to the sending unit.  If that's good then the sending unit itself needs to be removed and repaired or replaced.

-------------
Past AMC's
1974 Hornet X (new)
1975 Gremlin X (new)
1964 Classic 660 Cross Country
1965 American 440-H


Posted By: RebelYell
Date Posted: Feb/24/2016 at 4:27pm
Tony, I am afraid I can't give you any more update information on this topic, since I no longer own the car. Hope you find a solution to your problem.

-------------
http://s956.photobucket.com/user/dsheffie/media/DSCI05402_zps4c434594.jpg.html" rel="nofollow">


Posted By: tony matthews
Date Posted: Feb/29/2016 at 7:40am
Hi I need to replace my constant voltage regulator on my 78 matador barcelona. iv taken it apart and figure the wires look dark blue and probably burnt out ok so is there a replacement or similar I can use.I checked a hundred times the resistance from the sender unit to the gauge as long as i don't run the engine its reads constant ohms at the moment after putting the sender unit back into the tank and refitting the tank to the car and putting some fuel in it reads 27 ohms at any point from the sender to the back of the fuel gauge.So i reckon the wiring is fine and the earth . ok i did take the tank and sender unit out and connect it to the gauge by using additional wires and aS i MOVED THE FLOAT THE NEEDLE ON THE GAUGE MOVED ACCORDINGLY its ranged from approx 80 ohms to 20 ohms depending i believe when the float was in the full position the gauge in ohms was max out 80 ohms and at empty approx 20 ohms so I fit the whole thing back into the tank and turn the key ..NOTHING .after swearing a lot and thinking bollocks to this I turned back to the gauge and removed the oblong tin three pronged unit known as the CVR took it apart as the thing didn't seem to work and found the contacts the wiring  the wires look like burnt dark blue and figured that's the reaSON ITS NOT WORKING ITS BURNT OUT SO i NEED A REPLACEMENT OR SIMILAR UNIT TO FIT BACK IN THE PANEL WHICH AS YOU KNOW CONTROLS THE FUEL AND THE TEMP GAUGES help PLEASE THANK YOU tONY 


Posted By: 304-dude
Date Posted: Feb/29/2016 at 8:03am
Here is a diy, if you can obtain electronic parts near by, you can do this within a days time. It is for reference... I may have time today to do a step by step relay mod upgrade with a solid state IC and post it here. As I planned on doing it any way, just never got around to it for myself.

http://www.k-jet.org/articles/projects/instrument-cluster-voltage-regulators/" rel="nofollow - http://www.k-jet.org/articles/projects/instrument-cluster-voltage-regulators/

-------------
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker


Posted By: farna
Date Posted: Feb/29/2016 at 6:41pm
Here's a link to one on the back of a 64 Classic cluster. Real easy to do, if you can solder. Either mounting method works just fine.

The original regulator is a weird little thing! It doesn't deliver a constant 5V, but an "average" of 5V. Hook a digital volt meter to a good one and it will never find a reading, bouncing between 0V and 12V. An old analog meter needle will bounce, but isn't as fast, so should hover somewhere around 12V. It's a bi-metal strip that contacts, heats up and breaks contact, cools and contacts, heats up and breaks... ad infinitum (or until it doesn't...). When it fails it breaks contact, which is good for the sending units. 12V to them all the time wouldn't be good! So between the on-off sequences the average voltage is 5V, and average is good enough for the gauges to work. They work equally well with a constant 5V, and I suspect will last longer. The old CVR and sending units last a long time though, many 40 year old units are still working, so it's hard to tell if the constant voltage makes a difference or not, but it works and is an easy fix.


-------------
Frank Swygert


Posted By: captain eagle
Date Posted: Jun/01/2016 at 5:17pm
I have a 1981 AMC Eagle Limited Wagon !!! The fuel guage works and I have heat But Temp Guage doesn't work! Please tell how to get it w\to work!!! EHANK YOU VERY MUCH!!!


Posted By: captain eagle
Date Posted: Jun/01/2016 at 5:20pm
Originally posted by captain eagle captain eagle wrote:

I have a 1981 AMC Eagle Limited Wagon !!! The fuel guage works and I have heat But Temp Guage doesn't work! Please tell how to get it w\to work!!! EHANK YOU VERY MUCH!!!


Posted By: farna
Date Posted: Jun/04/2016 at 8:38am
First disconnect the temp sending unit and ground the wire to the block. If the temp gauge goes up to "HOT" (all the way up) the gauge is working fine, replace the sending unit. If not, make sure there is no break in the wire before replacing the temp gauge.


-------------
Frank Swygert


Posted By: White70JavelinSST
Date Posted: Jun/08/2018 at 4:24pm
Those parts that were talked about in this thread, that were being purchased at Radio Shack are now not available through the defunct Radio Shack,

Anyone found a new source?


-------------
70 Javelin SST, second owner, purchased 1972


Posted By: 6PakBee
Date Posted: Jun/09/2018 at 8:48am
Originally posted by White70JavelinSST White70JavelinSST wrote:

Those parts that were talked about in this thread, that were being purchased at Radio Shack are now not available through the defunct Radio Shack,

Anyone found a new source?


This is the only way to go.  I have not personally used one but I know of two friends that have and they are very satisfied.

http://rt-eng.com/rte/index.php/RTE_limiter" rel="nofollow - http://rt-eng.com/rte/index.php/RTE_limiter


-------------
Roger Gazur
1969 'B' Scheme SC/Rambler
1970 RWB 4-spd Machine
1970 Sonic Silver auto AMX

All project cars.

Forum Cockroach


Posted By: farna
Date Posted: Jun/09/2018 at 9:15am
Never heard of it called a "limiter" before, but I guess that's a Chrysler term for what AMC calls the IVR (Instrument Voltage Regulator). RTEs instructions for using an external regulator with the regulator built into the fuel gauge will work for AMCs made that way -- Hornets and Gremlins through about 77 or 78, 67-69 American/Rogue.

With Radio Shack gone there is no easy place to get small electronic components. You can order from several on-line places or Amazon though. Might cost you $7 to order a $2 part though. I recently needed a couple diodes for a repair -- no local source. Had to order a pack of $10 for $6 and pay $5 to ship, all for $2 worth of diodes it there had been a local RS.  Many cities still have electronics or HAM radio hobby stores, maybe you're lucky. I did a quick Google search and really couldn't find anything in Columbia SC. Might be some small shop somewhere...


-------------
Frank Swygert


Posted By: Lucas660
Date Posted: Jun/09/2018 at 9:38am
I would try Mouser for the L7805 regulator. Or call electronics repair shops locally. I have ordered L7824 and 7924 regs for audio projects from China for about a dollar but they take a while to arrive.


Posted By: InRogue
Date Posted: Sep/04/2018 at 7:02pm
Is this the same on earlier cars (regulator), my '66 American is the same way....no temp or gas gauge. 


Posted By: farna
Date Posted: Sep/05/2018 at 5:25am
Yes, there is a removable regulator on the back of the instrument panel on the 66. Looks like a little metal container, plugs in. Lucky you have a 66 -- starting in 67 the regulator is made into the fuel gauge and a lot harder to repair.


-------------
Frank Swygert


Posted By: amcenthusiast
Date Posted: Sep/05/2018 at 9:10am
Alright! Lets get our fuel and temp gauges working again YEA!

Thanks everybody for all the additional solutions and info.

-Now planning to fix REBEL/M-XRV8's fuel and temp gauges and will be doing pics and description over there in the 'Member's Projects' section.


-------------
443 XRV8 Gremlin YouTube video: https://www.youtube.com/watch?reload=9&v=2DmFOKRuzUc
XRV8 Race Parts website: http://amcramblermarlin.1colony.com/


Posted By: InRogue
Date Posted: Sep/05/2018 at 3:55pm
Originally posted by farna farna wrote:

Yes, there is a removable regulator on the back of the instrument panel on the 66. Looks like a little metal container, plugs in. Lucky you have a 66 -- starting in 67 the regulator is made into the fuel gauge and a lot harder to repair.

Thanks Frank I'll check it out


Posted By: InRogue
Date Posted: Sep/05/2018 at 5:26pm
Originally posted by farna farna wrote:

Yes, there is a removable regulator on the back of the instrument panel on the 66. Looks like a little metal container, plugs in. Lucky you have a 66 -- starting in 67 the regulator is made into the fuel gauge and a lot harder to repair.

Frank did some checking and it ended up being a bad connection at the fuse, a little cleaning of the terminal and all lights and gauges now work. Okay what's next on the list :) 


Posted By: farna
Date Posted: Sep/05/2018 at 5:42pm
Lucky you!! For those not so lucky, you can get replacement bi-metal regulators that just plug in, but the solid state regulator is a better choice. The bi-metal regulator gives a 5V average. You can't measure the voltage output with a digital VOM because it never stays the same. Even an old analog VOM will bounce between 0 and 12V. The "regulator" cuts on and off, and the average should be 5-6V. The gauges aren't real picky. A solid state 7805 regulator will provide a constant 5V. They don't have enough load to heat up under the dash. Mine has been in the car since 2002 or so, and it has traveled 70-80K during that time, and still works great. See http://sr-ix.com/AMC/dashreg/index.html" rel="nofollow - http://sr-ix.com/AMC/dashreg/index.html


-------------
Frank Swygert


Posted By: InRogue
Date Posted: Sep/16/2018 at 8:27pm
Found this tonight searching the inter web....might help someone out looking for one. 


Posted By: farna
Date Posted: Sep/17/2018 at 6:13am
$5 or so and some soldering will get you an electronic regulator though. If you simply must have it 100% stock then you have to spend the money. On things like this where no one would ever know unless they removed the instrument panel I wouldn't spend the money, but I do understand that many would just want to keep it all stock and working as original. Nothing wrong with either way. $50 shouldn't break anyone's resto budget either...


-------------
Frank Swygert


Posted By: Bob Mears
Date Posted: Dec/17/2018 at 10:05am
I installed one of these last year. Worked great until last Weekend. havent  taken the dash out again to see what going on.     
https://www.summitracing.com/parts/smp-vrc601?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-standard-motor-products&gclid=Cj0KCQiAr93gBRDSARIsADvHiOp6s7eL6jwfRRzRTBhnO3iad2iQntPUei69--3yb8K9xZyr96K1jecaAtUgEALw_wcB


Posted By: farna
Date Posted: Dec/18/2018 at 5:38am
The Standard product is likely made in Mexico. The problem with the low volume parts is that they are made by smaller companies, not actually by Standard. Quality varies. Fine for a show car, but if you drive a lot they don't typically last long. If Ron Francis Wiring has one I'd try them, as they typically use high quality parts. Scott Drake has electronic FORD style regulators that look original but have a solid state regulator inside, but won't fit AMC and I don't think they make a Chrysler/AMC part (I think Chrysler and AMC interchange). I've had a simple 5V regulator as I noted in a couple earlier posts (link to TomJ's site) in my car since 2003 with no issues at all, can't get more reliable than that!


-------------
Frank Swygert


Posted By: tunes12
Date Posted: Aug/09/2023 at 1:15pm
Does anyone have a step by step on how to add the voltage regulator? Some of the links in this thread no longer work and I'm having a hard time picturing what I need to purchase and where to attach. I have a 73 Gremlin with internal regulator in the temp gauge. I've cleaned the contact in there but no luck.


Posted By: nickleone
Date Posted: Aug/09/2023 at 4:38pm
Installed:   https://www.ramblerlore.com/AMC/dashreg/index.html" rel="nofollow - https://www.ramblerlore.com/AMC/dashreg/index.html



-------------
nick
401 71 Gremlin pro rally car sold
390 V8 SX/4 pro rally car sold
1962 Classic SW T5 4 wheel disc brakes


Posted By: tunes12
Date Posted: Aug/10/2023 at 6:22am
Thank you for that. While it helps understand the concept, I’m not clear on where to connect the wires I’m adding on my Gremlin board.


Posted By: farna
Date Posted: Aug/10/2023 at 7:56am
That link doesn't help the late model American (I think 67-69? I might be off a year either way on the start year...) and Hornet/Gremlin guys. I did a quick search and found this (line through words are corrections!):

"Starting in 68 all small car got the limiter built into the FUEL  TEMP gauge (checked the 68 TSM!). So 12V goes to the temp gauge, is limited to 5-6V, then is jumped from the 5-6V output over to the fuel gauge. The IVR in the link is for big cars and Americans made prior to 68 (might be 67... would have to look at the TSMS). So it's not doing you any good.   The fuels temp gauge has three studs -- ground, 12V, and 5V that jumps over to the two stud temp fuel gauge. You can disassemble the fuel temp gauge and break the 5V and 12V connections inside. Then you can run a solid state regulator (7805) outside the cluster. It can be mounted on the ground stud. The tab and the center pin are both ground, internally connected, so if you mount on the ground stud you can clip off the center regulator pin. Jump a wire from the 12V stud to the input of the regulator, then run a wire from the 5V output to the 5V stud. You will need a wire feeding the fuel gauge to come back to the 5V stud also.

The only thread I found where someone did this had broken links -- it's from 2011. Doc Creer (member name on here, should be current) said he did his..."


-------------
Frank Swygert


Posted By: tunes12
Date Posted: Aug/11/2023 at 2:49pm
Originally posted by farna farna wrote:

That link doesn't help the late model American (I think 67-69? I might be off a year either way on the start year...) and Hornet/Gremlin guys. I did a quick search and found this (line through words are corrections!):

"Starting in 68 all small car got the limiter built into the FUEL  TEMP gauge (checked the 68 TSM!). So 12V goes to the temp gauge, is limited
to 5-6V, then is jumped from the 5-6V output over to the fuel gauge. The
IVR in the link is for big cars and Americans made prior to 68 (might
be 67... would have to look at the TSMS). So it's not doing you any
good.   The fuels temp gauge has three studs -- ground, 12V, and 5V that
jumps over to the two stud temp fuel gauge. You can disassemble the fuel
temp gauge and break the 5V and 12V connections inside. Then you can run a
solid state regulator (7805) outside the cluster. It can be mounted on
the ground stud. The tab and the center pin are both ground, internally
connected, so if you mount on the ground stud you can clip off the
center regulator pin. Jump a wire from the 12V stud to the input of the
regulator, then run a wire from the 5V output to the 5V stud. You will
need a wire feeding the fuel gauge to come back to the 5V stud also.

The
only thread I found where someone did this had broken links -- it's
from 2011. Doc Creer (member name on here, should be current) said he
did his..."




^^^Super helpful. Thank you.

I did some further troubleshooting today and wonder if some of you here can help me wrap my brain around this. I took the cluster apart again. If I touch 12v to the temp gauge posts (quickly), I can see the temp gauge start to peg. So in my mind the IVR works. I then tested continuity between all 3 posts on the temp gauge. When I pull the contact apart inside the temp gauge, continuity goes away, as expected. I also checked continuity to the fuel gauge from the input side of the temp gauge, all the way through to both sides of the fuel gauge. No issues there as far as I can tell. Does this all mean the IVR is good?

Next, when I ground the temp gauge wire at the sensor to the block, it pegs the temp gauge, as I believe it should. When I ground the sender wire at the fuel tank, the fuel gauge also pegs. Good there as well, if I'm not mistaken.

I found the ground (black) wire of the main harness plug to the back of the cluster and confirmed continuity against a good ground on the car. I then confirmed continuity between all the grounds along all of the traces on the cluster. All good there as well.

Everything seems to work as it should, no? What would be the next step in troubleshooting? I'm out of ideas.


Posted By: bigbad69
Date Posted: Aug/11/2023 at 3:05pm
If "everything seems to work as it should", then I think you're done troubleshooting.

You can get movement out of the gauges by grounding the sense wires, so they're working fine as far as I can tell. If you have an accuracy problem, check the temp sensor or the ground for the fuel sensor. Those are the most likely suspects.


-------------
69 Javelin SST BBO 390 T10


Posted By: tunes12
Date Posted: Aug/11/2023 at 3:37pm
Originally posted by bigbad69 bigbad69 wrote:

If "everything seems to work as it should", then I think you're done troubleshooting.

You can get movement out of the gauges by grounding the sense wires, so they're working fine as far as I can tell. If you have an accuracy problem, check the temp sensor or the ground for the fuel sensor. Those are the most likely suspects.


Well they still don't work at all, which is why I don't believe I'm done troubleshooting. Lol.

Does the grounding of each and the fact that each gauge pegs when grounded confirm that they are getting the power they need? If not, I think I still need to figure out how to do that.


Posted By: worm611
Date Posted: Aug/12/2023 at 4:13am
Sounds like Voltage Regulator, grounding your gauge will still show movement on your needle even if the VR is going bad.  I fought with my temp gauge for awhile, and turns out it my Voltage Regulator was sometime..... not always working....  so I swapped it out for a solid state and been good since.

I fought with both the Fuel Gauge and Temp sensor for quite awhile, on my 70 Javelin after I first purchased it.

Installed a new sending unit (mine tested bad).  Fought with the horribly designed "Low Fuel Warning" circuit for awhile, turns out my relay is a bit flakey.  So a few issues in that circuit.  But got it working well after all.  Then I discovered a hole in my gas tank, so had to replace that..... just part of the fun with classic cars I guess :-)

Temp gauge had a few issues.  The violet wire going to the temp sensor had a brake in it some where, wouldn't show any continuity to from the cluster to the sensor, so replaced that.  Then to find out my Voltage Regulator was bad.  Replaced with a solid state VR, problem solved.

I'm not one that likes to just throw parts at a car, but VR's are not that easy for DYI'ers to trouble shoot, I would recommend at least pulling it out, and cleaning up the tabs on them if you don't replace it.

Jeremy


Posted By: tunes12
Date Posted: Aug/12/2023 at 5:53am
Originally posted by worm611 worm611 wrote:

Sounds like Voltage Regulator, grounding your gauge will still show movement on your needle even if the VR is going bad.  I fought with my temp gauge for awhile, and turns out it my Voltage Regulator was sometime..... not always working....  so I swapped it out for a solid state and been good since.

I fought with both the Fuel Gauge and Temp sensor for quite awhile, on my 70 Javelin after I first purchased it.

Installed a new sending unit (mine tested bad).  Fought with the horribly designed "Low Fuel Warning" circuit for awhile, turns out my relay is a bit flakey.  So a few issues in that circuit.  But got it working well after all.  Then I discovered a hole in my gas tank, so had to replace that..... just part of the fun with classic cars I guess :-)

Temp gauge had a few issues.  The violet wire going to the temp sensor had a brake in it some where, wouldn't show any continuity to from the cluster to the sensor, so replaced that.  Then to find out my Voltage Regulator was bad.  Replaced with a solid state VR, problem solved.

I'm not one that likes to just throw parts at a car, but VR's are not that easy for DYI'ers to trouble shoot, I would recommend at least pulling it out, and cleaning up the tabs on them if you don't replace it.

Jeremy


Please read my post from a few posts back. I’ve already cleaned the contacts. I’ve already tested all continuity and done some testing that I believe rules out the IVR. When I put 12v to it, I watch it heat up, and the garage moves. Same when I ground the temp sensor wire.

On to the fuel gauge. When I ground that, it also pegs. When it measure the resistance at the tank. I do get 650-1000+ ohms, so something seems off there. Need to investigate that one further.


Posted By: 6PakBee
Date Posted: Aug/12/2023 at 7:56am
Simplest test for a functioning IVR is to measure the voltage at the temperature sensor with the key on.  If everything is functioning, the voltage will fluctuate from +12V to 0v about two times a second.  This gives an average voltage of about 5v to the gauges. 


-------------
Roger Gazur
1969 'B' Scheme SC/Rambler
1970 RWB 4-spd Machine
1970 Sonic Silver auto AMX

All project cars.

Forum Cockroach


Posted By: tunes12
Date Posted: Aug/12/2023 at 8:30am
Originally posted by 6PakBee 6PakBee wrote:

Simplest test for a functioning IVR is to measure the voltage at the temperature sensor with the key on.  If everything is functioning, the voltage will fluctuate from +12V to 0v about two times a second.  This gives an average voltage of about 5v to the gauges. 


Just tested this. While I do have a digital multimeter that makes it difficult to confirm exactly 0-12v with that fast a speed, I do see it fluctuating to 12v+ and back down to 0v with a regular cyclical pattern. Still no functioning gauge though.


Posted By: Trader
Date Posted: Aug/12/2023 at 8:47am
If you have power, maybe you don't have ground.
Try taking the cover off the gauge cluster and running a wire from the cluster housing to the temperature gauge body and then a clean spot on the fuel tank.
If the gauges work, then you know you have ground issues somewhere between battery, gauge cluster, chassis, engine and fuel tank.


Posted By: bigbad69
Date Posted: Aug/12/2023 at 12:22pm
Originally posted by tunes12 tunes12 wrote:

Next, when I ground the temp gauge wire at the sensor to the block, it pegs the temp gauge, as I believe it should. When I ground the sender wire at the fuel tank, the fuel gauge also pegs.
This verifies the IVR is working, as are the sense wires. 

Both gauges are rated 9Ω full scale, and 75Ω for the low end reading. 

650 - 1kΩ in the fuel sensor means you will never register on the gauge. It sounds like you may have to pull the sensor from the tank and have a closer look.

The resistance of the temp sensor can also be measured. The TSM has instructions on this. Soaking it in boiling water (the sensor, not the TSM) should produce around 9Ω resistance.

Originally posted by tunes12 tunes12 wrote:

While I do have a digital multimeter that makes it difficult to confirm exactly 0-12v with that fast a speed, I do see it fluctuating to 12v+ and back down to 0v with a regular cyclical pattern.
That's exactly what you should see. The switching rate of the IVR is too slow for the meter, so the reading wanders whether on VDC or VAC setting.




-------------
69 Javelin SST BBO 390 T10


Posted By: 6PakBee
Date Posted: Aug/12/2023 at 5:03pm
Originally posted by tunes12 tunes12 wrote:

Originally posted by 6PakBee 6PakBee wrote:

Simplest test for a functioning IVR is to measure the voltage at the temperature sensor with the key on.  If everything is functioning, the voltage will fluctuate from +12V to 0v about two times a second.  This gives an average voltage of about 5v to the gauges. 


Just tested this. While I do have a digital multimeter that makes it difficult to confirm exactly 0-12v with that fast a speed, I do see it fluctuating to 12v+ and back down to 0v with a regular cyclical pattern. Still no functioning gauge though.


Use a test light.  But it seems your IVR is functioning.  Thermal gauges are fed by the IVR and then are connected to the sensor.  If you have voltage at the temperature sensor but yet the gauge doesn't work, you either have a bad gauge or a bad sensor.  The voltage at the sensor has to go through the gauge.  


-------------
Roger Gazur
1969 'B' Scheme SC/Rambler
1970 RWB 4-spd Machine
1970 Sonic Silver auto AMX

All project cars.

Forum Cockroach


Posted By: farna
Date Posted: Aug/13/2023 at 3:55pm
Make sure the instrument cluster is well grounded. You might need to run an additional ground wire from anywhere on the cluster there is a ground to somewhere metal under the dash. The temp sender grounds to the block. Make sure you didn't use teflon tape or sealer on it! The gas tank grounds to the body through the top of the tank where it contacts the bottom of the trunk floor. That rusts a little and messes up the ground. I always clean the fuel outlet nipple and solder a wire around it, running that wire to the body nearby, grounding the sending unit. This eliminates a bad ground through the tank.


-------------
Frank Swygert


Posted By: tunes12
Date Posted: Aug/14/2023 at 8:25am
I'm back to thinking it's the IVR, but it's hard for me to know why it's bad. When I bring the gauge over to me bench and hook 12v to it, I expect the contact point to move quickly, switching from 12v to 0v. It does not do that. It'll peg the gauge, heating the wire to point of smoke...which I assume is bad. The contact element point never bends away from the 12v contact point. Strange as it appears to switch from 12v to 0v at the sensor side when in the car.

I don't mind getting aftermarket gauges (I've ordered them already), but I have a hard time giving up not knowing exactly what's wrong with the current setup. I'm to the point now where I'm just going to say it's a bad IVR and move on.


Posted By: 6PakBee
Date Posted: Aug/14/2023 at 9:14am
From what you describe, you are putting 12v to the gauge and grounding the sensor lead.  Doing this never energizes the IVR heater and you'll have a constant 12v going to the gauge.  This is a crude drawing of what I THINK is the gauge wiring.  If you are trying to bench test the gauge, apply 12v to the gauge and ground the gauge case.  Nothing else.  You should see the IVR functioning and you should have the pulsating voltage at the sensor connection. 




-------------
Roger Gazur
1969 'B' Scheme SC/Rambler
1970 RWB 4-spd Machine
1970 Sonic Silver auto AMX

All project cars.

Forum Cockroach


Posted By: farna
Date Posted: Aug/15/2023 at 8:02pm
Yeah, letting the smoke out is bad!! The IVR quickly switches on and off, faster than a turn signal blinker (sort of like the blinker when a bulb is burned out). You really shouldn't be able to clearly see the on and off points, just a jumping needle (analog gauge) or fluctuating reading on a digital gauge, but shouldn't go over 12V much under 5V -- just bouncing between the two. 

6PakBee calls it a "heater", and that's about right. It's a bi-metal strip that heats and cools rapidly, which causes it to flick on and off rapidly. With all that movement it's easy to see how it wears out and breaks (or sometimes slows down, or sticks open or closed) over a period of 30-50 years!


-------------
Frank Swygert


Posted By: mramc
Date Posted: Aug/31/2023 at 6:48pm
Ok, I think this has been mentioned before there a company that makes a solid state Instrument Cluster Voltage regulators . Seems mopars have this problem also. Some  mopars used the ICVR that AMCs use use along with some Fords Mustangs I believe for one. The company is real time engineering 
https://www.rt-eng.com/index.php/IVR4_Limiter_List.html" rel="nofollow - https://www.rt-eng.com/index.php/IVR4_Limiter_List.html . The IVR4 works in a lot of AMCs per there list. I have one in my 1974 Matador coupe and works well. A little bit more expensive then the point type ICVR but not by much and the old point type you never know what your getting china junk or some that been rusting on shelf for 50 years. LRDaum


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LRDaum



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