1982 coolant gauge issues
Thread Starter
Racer
Joined: Oct 2021
Posts: 436
Likes: 15
From: Maryland
1982 coolant gauge issues
Hello, coolant gauge reading was off for me starting today. Randomly jumped between like 180 (which is what it was supposed to be at) to 100, and back. Diagnosis is follows:
1. Plugged in scanner to car, car computer temp reads accurately
2. Took cluster off, bench tested the gauge itself using a potentiometer, good on all ranges.
3. Continuity tested the connection between the gauge screws and their associated pins on the female connector end on the cluster, good there too
4. Continuity tested the ground pin on the male connector that goes to the cluster, good
5. Tried to continuity test sender pin on the male connector to coolant temp sensor pins, nothing
Questions are as follows:
1. Should number 5 above ^ have worked? Idk if it should've, it was kinda a shot in the dark
2. The factory repair manual mentioned disconnecting the connector at the "Rear Compartment". What is that?
3. I know that the temp sending unit is good, and I know that the gauge is good. How do I test wiring? Diagrams would be appreciated.
4. How else can I test this to see what's wrong?
Thank you all.
1. Plugged in scanner to car, car computer temp reads accurately
2. Took cluster off, bench tested the gauge itself using a potentiometer, good on all ranges.
3. Continuity tested the connection between the gauge screws and their associated pins on the female connector end on the cluster, good there too
4. Continuity tested the ground pin on the male connector that goes to the cluster, good
5. Tried to continuity test sender pin on the male connector to coolant temp sensor pins, nothing
Questions are as follows:
1. Should number 5 above ^ have worked? Idk if it should've, it was kinda a shot in the dark
2. The factory repair manual mentioned disconnecting the connector at the "Rear Compartment". What is that?
3. I know that the temp sending unit is good, and I know that the gauge is good. How do I test wiring? Diagrams would be appreciated.
4. How else can I test this to see what's wrong?
Thank you all.
Safety Car
Joined: Nov 2005
Posts: 3,532
Likes: 1,185
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Best advice right now is to purchase a 82 GM service manual that has ALL the diagrams that you need to accurately troubleshoot this issue. Does the engine run and idle just fine and just an intermittent indication issue?
Thread Starter
Racer
Joined: Oct 2021
Posts: 436
Likes: 15
From: Maryland
Safety Car
Joined: Nov 2005
Posts: 3,532
Likes: 1,185
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
If you are wanting to troubleshoot the wiring and integration you are looking at the wrong manual. AIM will NOT help you. Purchase a 82 GM service manual.
Thread Starter
Racer
Joined: Oct 2021
Posts: 436
Likes: 15
From: Maryland
have both, read both thoroughly. I think I may have found the issue. Apparently the sender going to the gauge is diff than the one going to the ecm?? Manual nor AIM mentioned that, even in the circuit diagrams.
Race Director
Joined: Nov 2006
Posts: 13,193
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From: Sunshine Coast, Queensland, Australia
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The Electrical Troubleshooting Manual is the one that breaks down every circuit. This manual must be added to your collection. Mine certainly is worn.
Safety Car
Joined: Nov 2005
Posts: 3,532
Likes: 1,185
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
I have never seen a wiring manual like your 77 for the 82. I believe 78 was the last year for that from GM. The 84 does have a supplemental wiring manual though. In my 30 years with CFI, I have never seen a dedicated GM wiring manual for the 82 which would be great. The wiring for the water temp is not rocket science just because it's a corvette. They have been using the same basic system for a long time with slight variations over that time. If you find that GM wiring manual, let me know...I would want one. 
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Melting Slicks
Joined: May 2021
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From: Fleming Island, FL
Yes, they are two separate things. They are called sending units when used for the gauges and sensors the ECM's.