Yes, another PCM issue. My 2008 H3 Base Model has 74000 on it. I can drive it all day long with the AC on, but when I leave work at night, I turn the AC off after start up. Within 15 minutes of driving, the temp gauge drops to zero and I get an AC OFF message on the dash. If I stop and pull the PCM-B fuse and put it back my temp gauge and ac work again with no overheat issues. The temp is always normal. I tried changing the temp sending unit and there was no change. This only happens at night.

A few additional facts, I have not replaced the battery in the vehicle yet, it's at least 3 years old. Also I just started getting a P0303 code. I have not been able to swap plugs and wires yet due to rain.

Finally, every so often when I start the vehicle, it engine revs then drops almost to stall, then revs again and finally levels off. I have cleaned the throttle body in the past to solve that issue, but it returned within a year.

Any and all help is appreciated!!!! I tried to give enough detail but let me know if there are questions.

 

Hi did you end up fixing this? I have the same problem?

Any help would be appreciated

 

It turns out that the head had to be replaced to solve the misfire issue and the thermostat had to be replaced to solve the under-cooling. This was all per the dealer who had the car for almost a month. Between the dealer and the warranty company, it took them 27 days to figure it all out. Final cost was $4200. They also had to replace the radiator.

 

ooh, and they broke every single head bolt in the process...

 

So changing the thermostat fixed the ac problem? Or would I have to change to temp sensor as well? Cuz I'm getting the ac off message every now and then. I live in texas so need to get this fixed ASAP before the summer really hits.

 

The AC OFF message is NOT an AC problem, it is the first layer of overheat protection and the DIC is telling you the PCM shut off your AC to avoid an overheat.

This can happen due to many reasons: bad temp sensor, bad T Stat, bad coolant (old and/or contaminated), crud caked radiator, bad clutch fan, bad radiator .... etc.

In order to answer your question we would need more info, way more. What does your temp gauge read when the AC OFF message appears, have you have it scanned so you know what the actual temp is?

 

The temp gauge doesnt read anything, it just drops all the way down. That's when the ac quits blowing cool, and the message appears. It will randomly come back on, on its own, and the temp is normal. Haven't had it scanned. Just trying to figure out the problem so I can try to fix myself. Taking it somewhere just costs to much. Thanks for the info.

 

You can try a new temp sensor, they are cheap and easy. If that doesn't do it, you are only out the $22 and 15 minutes for the new sensor.

See this thread: https://www.hummerforums.com/forum/h...tart-up-32663/

 

on old cars when the coolant was low the sensor was out of the juice and the gage read LOW! when the engine was HOT

 

I have this issue with the temp gauge in the dirt and the AC Off indication. Can someone please tell me where this temp senser is located and how easy or hard it is to replace. Photos would be good. My tempature seems good but if its because the thermostat. how much $$$ does it cost to replace and should you replace the water pump too? water pumps and thermostats can cost engines. need as much details as you can provide! thanks in advance!