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Temp and Fuel Gauge don't work

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farna View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post 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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tunes12 Quote  Post ReplyReply Direct Link To This Post 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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 6PakBee Quote  Post ReplyReply Direct Link To This Post 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
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1970 RWB 4-spd Machine
1970 Sonic Silver auto AMX

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farna View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post 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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mramc Quote  Post ReplyReply Direct Link To This Post 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 . 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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