Troubleshoot Bad HVAC Controls

jimlem · July 22, 2012

I'm hoping someone here with the technical know-how or a similar experience can help figure out my truck's crazy AC operation. It's an '02 Silverado 1500HD 6.0L, with the manual HVAC controls (not the dual zone climate control). For the past few months, I've had the problem of random switching of cold to hot air when the AC is on. I've also noticed the system seems to change at random to and from Fresh Air to Recirculate. But when it does, both the fresh and recirc lights are on together. I was once told by a trusted shop that it was impossible for both to be on at once on my truck but it happens many times a day. Anyway, I collected every bit of info I could from past posts here and other sites. I ended up replacing the temperature blend actuator and calibrating the system. I found my problem still exists but I'm thinking it may actually be the controls themselves.

Here's why: When I first start up the truck with all HVAC controls turned off (all full counter-clockwise), I hear the various actuators whirring and moving their respective parts. This goes on forever. As long as I sit idling, it continues. It begins with each motor (in turn) running for a few seconds, then the AC comp will cycle on for 1 to 2 seconds, then the 3 amber LEDs on the HVAC panel will flash in various patterns. There doesn't seem to be any set pattern. Sometimes all 3 lights flash one to three times. Sometimes just the Fresh or Recirculate light comes on and the AC light turns on or off a couple of times. If I sit idling this process will continue to repeat over and over but very few "cycles" happen exactly the same. LAST: When I was working on the temp actuator, I checked the Recirculate actuator motor's operation and it seems fine. I was able to watch it thru the back of the glovebox with a flashlight and it's normal. HOWEVER- when my system messes up and starts blowing hot air while on AC, I ALWAYS see BOTH Fresh and Recirculate lights on. Whenever I look down and see both those lights on I know one of two things will quickly follow. It will either switch from fresh to recirculate (or vice versa, i.e. the opposite of the current setting) or, it will switch from cold air to full heat. While sitting and watching the recirculate actuator/door the system messed up a few times. I was able to see the recirculate door move whenever the 2nd light came on. It's almost like my actuators are getting ghost signals from somewhere rather than being defective themselves.

Any ideas would be greatly appreciated.

Carder09 · July 22, 2012

I would try finding another A/C control panel and slaving it in, Seems as though the controls are to blame for the mess your'e having.

jimlem · July 22, 2012

Thanks for the reply. I found a couple online sources (GM Parts Direct and Amazon) that have them but I don't want to wait a week to get it. I'll call local dealers 1st thing Monday and just go buy one. Hopefully before I pull out my (very thin) wallet someone who has done the job will chime in with a for sure answer on the controls being to blame. Or I'd settle for just knowing why/how all the lights cycle on and off every startup. Thanks again Carder.

bossier62guy · July 22, 2012

You're not going to get an answer like that here with the problem you're having. From what you've described the control panel is where I'd be going next as well. If your wallet is that thin maybe you could check out some used parts online or at a local salvage yard. Have you tried disconnecting the battery?

jimlem · July 23, 2012

You're not going to get an answer like that here with the problem you're having. From what you've described the control panel is where I'd be going next as well. If your wallet is that thin maybe you could check out some used parts online or at a local salvage yard. Have you tried disconnecting the battery?

I appreciate the input. I don't know why I wouldn't find any help here. This is where I found all the helpful info on changing out the temp actuator motor. Anyway, it's not that my wallet is too thin to afford a new part, the part is no longer available for purchase anywhere near me. It seems GM stopped making them and the dealers are directed to send the defective part out to a local auto electric shop for rebuild. This doubles the original cost and takes a min. of 2 weeks to get back. Given all the time and trouble, I was looking for reassurance I was headed in the right direction, not a low cost alternative. I'd gladly pay for a new one if there was one.

asc08 · July 24, 2012

You may want to contact one of the outfits that rebuilds gauge clusters. Do a search, there are a couple that come recommended. Don't know if they will rebuild the module, but others have used them to replace the backlight bulbs in components other than the gauge cluster. Worth a shot...

bossier62guy · July 24, 2012

You're not going to get an answer like that here with the problem you're having. From what you've described the control panel is where I'd be going next as well. If your wallet is that thin maybe you could check out some used parts online or at a local salvage yard. Have you tried disconnecting the battery?

I appreciate the input. I don't know why I wouldn't find any help here. This is where I found all the helpful info on changing out the temp actuator motor. Anyway, it's not that my wallet is too thin to afford a new part, the part is no longer available for purchase anywhere near me. It seems GM stopped making them and the dealers are directed to send the defective part out to a local auto electric shop for rebuild. This doubles the original cost and takes a min. of 2 weeks to get back. Given all the time and trouble, I was looking for reassurance I was headed in the right direction, not a low cost alternative. I'd gladly pay for a new one if there was one.

Mainly because of the issue you're having....it's tough to troubleshoot a problem like that via the internet. I've got an 02 as well and have had a blend issue w/ my system for years. It's not that bad so I just deal with it but i've been down the road of throwing money at it. Replaced one actuator and the HVAC control as well....no dice yet. The next suspect actuator cost too much to just try w/o knowing for sure so I know how you feel. Personally I wish they would have never gotten rid of the darn cables....never had one issue with those.