Weird AC Behaviors

ericag02 · August 29, 2006

I took my '04 Silverado LT into the dealer about 2 months ago because my AC until was making a strange noise in the cab. It honestly sounded like a leaf or something was being blown against the intake or something. Anyhow, they apparently couldn't hear it or didn't care (the output of the air was reduced as well).

So, they found a TSB (I believe) that had some reprogramming for the automatic AC unit in my truck. Ever since then my AC has been doing some weird things. Such as:

Turning the driver's side AC to MAX heat and not allowing any adjustments to be made to the driver's side AC until the truck stops and is completely turned off and back on again (this has happened 4 times now, and being in Texas during the summer, it's not a great thing to experience).

Or when it is cooling down the truck in 98-104 degree weather, it decides that the truck is cool enough after about 3 minutes. Mind you I have the AC set to 71 degrees at all times, expecting the air output to be substantial. It will turn off the Recirc and then lower the fan motors to about 1/4 speed so the air is just trickling out while I'm sweating inside.

Also, I noticed this recently as well. When driving at slow speeds and coming to stop signs my AC compressor turns off until I reach about 10MPH and then it turns back on. Then when I slow down again to a stop it does the same thing. I can sit at a stop sign for 3-4 minutes and the compressor stays off.

Has anyone had similar problems or heard about this reprogramming of the AC unit? I just don't want to seem like the crazy guy at the dealership when I drop the truck off again for them to undo their reprogramming and fix whatever is happening to cause these issues.

Thanks!

mmmikkke · August 29, 2006

This is why I am always fearful of new software being downloaded into my truck by out-of-touch do-gooders at the dealer. Sad thing is, you can never go back to the previous version of the software.

There have been posts about a/c units not working when the outside temperature gets too high. More software, apparently, deciding what is best for you.

Sounds like maybe they reprogrammed the a/c brain to only turn itself off during conditions where the engine is likely to need max cooling for itself, such as when travelling below 10 mph.

The more automated these trucks get, the more drunk-with-power the GM software engineers get!

You've seen a few posts of people going back to earlier versions...I pity the future owners of the GMT900's.

67ChevyRedneck · August 29, 2006

Funny you should post this. I took my truck in for 2 recalls yesterday. They fixed them and I needed my computer updated for the fog light program and they were already charging me $88 so I told them to go ahead and upload any "fixes" that were there. I drove my truck this morning and the "service 4wd" light comes on. WTF? I used it 3 days ago. I turned the truck on and off a few times and it worked once, but then not again. I'm going to unhook the battery when I get home and see what that does, if that don't work I'll see if any of the pins are disconnected in the switch, then replace the switch if that don't work?

What sucks is my truck is out of warranty and if I brought it back today I'd just get the "we didn't do it" speech. I refuse to bring my vehicle to any dealer unless it is absolutely necessary.

Edit: unhooked the battery.... fixed for now