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Temp and Fuel Gauge don't work |
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mramc
AMC Addicted Joined: Jul/12/2007 Location: United States Status: Offline Points: 3223 |
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Posted: Aug/31/2023 at 6:48pm |
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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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LRDaum
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farna
Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19692 |
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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!
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Frank Swygert
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6PakBee
Supporter of TheAMCForum Charter Member Joined: Jul/01/2007 Location: North Dakota Status: Offline Points: 5458 |
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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. |
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Roger Gazur
1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX All project cars. Forum Cockroach |
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tunes12
AMC Fan Joined: Mar/23/2023 Location: FL Status: Offline Points: 24 |
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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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farna
Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19692 |
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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.
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Frank Swygert
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6PakBee
Supporter of TheAMCForum Charter Member Joined: Jul/01/2007 Location: North Dakota Status: Offline Points: 5458 |
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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.
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Roger Gazur
1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX All project cars. Forum Cockroach |
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bigbad69
Supporter of TheAMCForum Joined: Jul/02/2007 Location: Ottawa, Ont. Status: Offline Points: 6686 |
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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.
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69 Javelin SST BBO 390 T10
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Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6913 |
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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.
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tunes12
AMC Fan Joined: Mar/23/2023 Location: FL Status: Offline Points: 24 |
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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. |
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6PakBee
Supporter of TheAMCForum Charter Member Joined: Jul/01/2007 Location: North Dakota Status: Offline Points: 5458 |
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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.
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Roger Gazur
1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX All project cars. Forum Cockroach |
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