HELP !! TEMPERATURE GAUGE IS HAUNTED BY GHOSTS !!&#33

Supreme Pizza · June 21, 2017

2002 Suburban 1500 LS 4x4 5.3

Issue: Temperature gauge works intermittently, with strange symptoms.

Details:

Essentially useless..

When you start it up cold, it will go up a tiny bit but wont go over 160.

Sometimes it works normally on startup, and reads properly.

Out of the blue it can start or stop working.

Sometimes you turn the key on, and it reads normally but after you start the engine it quickly drops to 160 and stays there.

Works normally for days, stops working for days.

Faulty temp sensor code came up once, but didn't come back after clearing the codes.

Vehicle may be running rich, smell of fuel in the exhaust sometimes.

Checked the electrical connector

Replaced the temp sensor (front left of the motor, by the exhaust manifold).

Tried banging on the instrument cluster

No coolant leaks or other cooling system issues.

Has a block heated installed.

As a mechanic, I HATE driving around without knowing my engine temp. Please throw out some ideas. Running out of options, and I don't want to go with an aftermarket gauge setup.

dsr611 · June 21, 2017

Try having the cluster rebuilt with new stepper motors and lighting. The stepper motors in that series of GM trucks and SUVs (and some cars I think) are notorious about going bad...and there's no rhyme or reason as to which one will go first.

$125 or less can get it rebuilt

Colossus · June 21, 2017

Ditto

Supreme Pizza · June 21, 2017

I understand that the stepper motor might be bad, but I would have to verify that is the problem before replacing the part. My question is this: What else could it be besides the stepper motor? How to test a stepper motor? If it was the stepper, why would it have such odd symptoms? Most electric motors work or they don't work. I think I may have a bad electrical ground somewhere on the wiring harness. A rusted out frame ground or something. Ideas?

dsr611 · June 21, 2017

When the stepper motor went out on my wife's Tahoe, it was the MPH stepper motor, You could be driving at 65 mph and needle would go up over 100 mph then a little later go down to 20 mph. Some days it would work as it should, other days it would fluctuate. I was researching the issue with it and found the info about the stepper motors. A few days before I got it fixed, the oil psi gauge and temperature gauge started doing the same thing...read fine one minute, then read abnormally high or low, work some days, and not work other days. Took it to a guy I knew from another message board and he replaced all the stepper motors and replaced all lighting with new LED lighting. Everything has worked fine since then.

Supreme Pizza · June 21, 2017

Hi, thanks for the info. I have determined that the stepper motor and the temp sensor both work properly. What ever the problem is, its somewhere else in the system. So besides the stepper motor and sensor what else could it be? The electrical connectors on the sensor and gauge cluster are in good shape. Its not the thermostat, or low coolant.

Mike GMC · June 23, 2017

Have you hooked up a scanner? Mine will allow me to display the temp the computer is seeing through the OBD II port regardless of what the dash gauge shows.

Supreme Pizza · June 24, 2017

The solution has been found.

During the spark plug change, a heater hose connection was broken. Some fluid was lost. That part was replaced.

During the block heater installation, some fluid was lost.

The over flow jug was always kept full, however - that was insufficient. The bleeding procedure needed to be followed exactly to the letter. Turns out that there was air trapped in the system, specifically around the temp sensor. The temp sensor reacts to temperature changes much faster than anticipated, which complicated the diagnostic process.

Bottom line, I bled the system per the Chilton's repair manual procedure, resulting in normal temperature gauge operation.

Dnt · June 29, 2017

Hey Boss glad you got that fixed up. Strange how air in a system where it does not belong can cause issues isn't it?

Posted in another thread about AC repairs by this same mechanic quote - "Air in the system will not cause any issues. Repair shops say that in order to get your money. I have never "vacuumed" the air out of any A/C system that I have ever worked on, and they all functioned just fine. My current vehicle needed several A/C repairs when I got it. For instance, one of the hoses was disconnected, so i'm sure there was some air in the system. I fixed everything, and added coolant until the pump kicked on (low pressure switch). Then I kept adding more until the pump kicked off (high pressure switch). Then I bled off some pressure until the pump stayed on at all RPM ranges. Done. Fixed. All you need to do is get the pressure level between the HI and LOW pressure switches, and it will work properly. Air in the system, or a little too much /too little coolant is not an issue. If you go to an A/C shop, they will say i'm totally wrong and that you need to pay them thousands of dollars to fix your air conditioner "properly". My knowledge is based on research and hands on experience. You may disagree with me, but it does not mean that your opinion is correct, or mine for that matter. Stop spending so much time picking apart others people posts, and focus more on helping the person in need.

LMFAO

e_schott · June 29, 2017

Hey Boss glad you got that fixed up. Strange how air in a system where it does not belong can cause issues isn't it?

Posted in another thread about AC repairs by this same mechanic quote - "Air in the system will not cause any issues. Repair shops say that in order to get your money. I have never "vacuumed" the air out of any A/C system that I have ever worked on, and they all functioned just fine. My current vehicle needed several A/C repairs when I got it. For instance, one of the hoses was disconnected, so i'm sure there was some air in the system. I fixed everything, and added coolant until the pump kicked on (low pressure switch). Then I kept adding more until the pump kicked off (high pressure switch). Then I bled off some pressure until the pump stayed on at all RPM ranges. Done. Fixed. All you need to do is get the pressure level between the HI and LOW pressure switches, and it will work properly. Air in the system, or a little too much /too little coolant is not an issue. If you go to an A/C shop, they will say i'm totally wrong and that you need to pay them thousands of dollars to fix your air conditioner "properly". My knowledge is based on research and hands on experience. You may disagree with me, but it does not mean that your opinion is correct, or mine for that matter. Stop spending so much time picking apart others people posts, and focus more on helping the person in need.

LMFAO

New to this forum so maybe I shouldn't say anything, but as an auto repair professional I can say that any technician that doesn't know about purging air from cooling systems, or evacuating AC systems with a vacuum pump is either very green in the field, or not very good at their profession..."Mechanic" is a loose term now a days I guess....

Dnt · June 29, 2017

I probably should not have done that but he was really pushing the AC issue about not doing a proper vacuum on another thread and THEN I saw this cooling system post he had made. I just could not resist the temptation. Too many adult beverages tonight I guess. Sorry stardude8tdc if I embarrassed you. Peace out brother........it is just a forum

Supreme Pizza · June 29, 2017

The cooling system for the engine and the A/C system are not the same. Two different systems.

Would it be ideal to get all of the air out of the system? Of course it would. Why? Because its not supposed to be in there. I'm explaining how to get the A/C system running for $20. If you know another way to do it for $20, please tell me. A repair shop is not going to remove the air from the system cheaply. If they did do it cheaply, then YES, get it done before adding coolant, why wouldn't you?

Supreme Pizza · June 29, 2017

Perhaps I should reply to questions this way:

Cheapest: Duct tape the hose

Proper: Replace the hose

Best: Go to the dealer

Is that better? Should I specify the 3 options with each response? I usually post the absolute cheapest easiest fix. I assume they already know the proper way to do it, such as going to the dealer.

Supreme Pizza · June 29, 2017

New to this forum so maybe I shouldn't say anything, but as an auto repair professional I can say that any technician that doesn't know about purging air from cooling systems, or evacuating AC systems with a vacuum pump is either very green in the field, or not very good at their profession..."Mechanic" is a loose term now a days I guess....

These other guys were suggesting that I rebuild the instrument cluster for over $100. Would that solution satisfy you? I fixed the cooling system for free, by the book. Whats the problem? I diagnosed, and solved the problem according to the Chilton's repair manual instructions. The A/C procedure im talking about is the only way to get the system running for $20 total. Do you know another way to make cold air for $20 AND remove the air from the system at the same time, because I would love to know how. Again - YES removing the air from the system would be ideal, but its not required in order to make cold air come out of your vents.

e_schott · June 29, 2017

These other guys were suggesting that I rebuild the instrument cluster for over $100. Would that solution satisfy you? I fixed the cooling system for free, by the book. Whats the problem? I diagnosed, and solved the problem according to the Chilton's repair manual instructions. The A/C procedure im talking about is the only way to get the system running for $20 total. Do you know another way to make cold air for $20 AND remove the air from the system at the same time, because I would love to know how. Again - YES removing the air from the system would be ideal, but its not required in order to make cold air come out of your vents.

No, because rebuilding the cluster would not have fixed the issue in the first place. It's good that you got it fixed. What rubbed me wrong is where you said you were a "mechanic". When you give people the impression that you do this kind of stuff professionally, some will take your word over the internet as gold. So it becomes a problem when you spread wrong info, or dangerous info, and people believe you because you are a "mechanic". I am not trying to be rude honestly, and maybe I should bite my tongue, but I am just saying I find it hard to believe a mechanic had to come to a forum for help in diagnosing what to most technicians is a simple issue to diagnose that is all.