'05 Silverado Dual Zone Ac Problem

jgillott · August 2, 2007

Yesterday, the dual zone AC in the '05 Silverado began to blow hot air out of the drivers side vents only. The passenger side continued working correctly. Every heat/cooling setting tried would blow hot air only on the drivers side. After shutting the truck off and restarting, it began working correctly again. Any Ideas of were to begin?

OUMike · August 2, 2007

Yesterday, the dual zone AC in the '05 Silverado began to blow hot air out of the drivers side vents only. The passenger side continued working correctly. Every heat/cooling setting tried would blow hot air only on the drivers side. After shutting the truck off and restarting, it began working correctly again. Any Ideas of were to begin?

Hmm. I would think that those would be controlled by two separate relays. I know on the older ones the AC relays are behind the glove box, may wanna start there. Could also be those control heads. My mother's 2000 Corvette has a dual zone (maybe the same one?) unit also, and I believe they've experienced some trouble with the control head.

Buggle_96 · August 2, 2007

This happens to me everytime I swap out my PCM. It takes 6-9 restarts. It blows pure hot air. Then drivers side will start to work right. And after a few more restarts the pass side starts to work. Weird, but my brothers 04 does the same thing.

curly · August 2, 2007

The same thing happened on my '03 but the drivers side blew cold while the passenger side was hot (my wife didn't like that too much ). The dealer fixed it under warranty.. they replaced the control module.

sledr · August 2, 2007

My 04 does this also - it is the HVAC system defaulting to defrost mode. There is a bulletin for this problem. Here is what's going on - there is a wire harness that rubs on a brace behind the instrument panel and causes a short. Mine was fixed under warranty but it just acted up on the way to the cottage last week. It sure was uncomfortable!!! Pulled off the highway for 10 minutes and when I restarted it the problem was gone.

Here is the number:

HVAC System Cannot Be Controlled Or Defaults To Defrost Mode (Repair HVAC Actuator Harness) #04-01-38-008 - (06/17/2004)

Hope this helps

jgillott · August 3, 2007

My 04 does this also - it is the HVAC system defaulting to defrost mode. There is a bulletin for this problem. Here is what's going on - there is a wire harness that rubs on a brace behind the instrument panel and causes a short. Mine was fixed under warranty but it just acted up on the way to the cottage last week. It sure was uncomfortable!!! Pulled off the highway for 10 minutes and when I restarted it the problem was gone.
Here is the number:

HVAC System Cannot Be Controlled Or Defaults To Defrost Mode (Repair HVAC Actuator Harness) #04-01-38-008 - (06/17/2004)

Hope this helps

Thank you very much for the information everyone. The truck is out of warranty due to the mileage, but this gives me what I need to start looking. Thanks again.

Mike1010 · August 16, 2007

Hello Readers. New to this forum.

I have a 2001 Tahoe with 125K on it. 5.3L, 4WD, 4DR, LT(AutoRide).

My problem is an AC system failure. I have read hours of related postings and decided to post this message.

#1 For a little over a year now my AC compressor has made a bit of a knocking noise when it cycles on. I didnt think much of it since the AC was working fine and I have heard this noise in other vehicles.

#2 Late last summer I noticed that my rear AC was not working, I also noticed a fast ticking noise which I thought was my fan blower. The noise occurs during idle or driving and only when the fan blower is on. It didn't seem to matter if the AC was on or not. I figured I would replace the fan motor when it failed.

#3 Since the beginning of this summer I noticed a decrease in AC performance. During a long road trip I had the AC blowing for about 3-4 hours. When I stopped to refuel I heard a hissing noise coming from the AC compressor area. I could not see what was leaking, but I am almost certain it was the refrigerant. When I got back on the road I noticed my AC was no longer cooling and the ticking noise was gone. Since my blower is still working fine, I figured that the noise was coming from the compressor. I assume that the ticking noise was the compressor and since the refridgerant leaked out, the compressor would not longer engage.

Findings:

The belt is in place and in good condition.

The compressor will engage when jumpering out the senor plug from the aluminum cylinder thingy (what do they call this thing). When I jumper the plug just for a second the entire engine wants to stall. I am assuming that the compressor is seized up at this point.

One other point to mention. Most of last summer I used to get this "jack hammer" noise when accelerating. I thought that it was my transmission. It seemed to occur on the first drive in the AM and after sitting for a while. It only seemed to happen when it was extra hot out. This noise has not occured since the season changed last fall, but it has occurred once this summer prior to the AC failure. Could this be related to the tension pully issue?

Questions:

#1 If the ticking noise was coming from the compressor, then why would it occur whenever I was just running the fan blower in heating mode? Someone told me that in newer vehicles it is designed to run when the blower is on. This way the compressor wouldn't sit unused for 9 months out of the year.

#2 Do you think I should plan to replace the compressor and procede with an entire AC system overhaul?

#3 If a system overhaul is advised, then can you point me to a good site that may assist me if I choose to procede to do the work myself.

Thanks for reading my post. Sorry it is so lengthly; I wanted to get the details out there.

Mike in Montana

dknarnd · August 16, 2007

Had this happen to me this summer on my 04 Sierra where after driving a couple hours the driver side started cranking out hot air. Finished the trip with the windows down and air off then parked the truck for a day, next time I started it up it was fine. It was still under warranty at the time so I took it in and the dealer did a reprogram of the AC. Of course the problem could not be recreated so this was probably just a standard try and fix it routine.

scottknight · August 23, 2007

So, did you get to the bottom of this? I am trying to track down why my 05 Tahoe only blows warm air out of the dash vents. The A/C system is working fine, though it was just a touch low on refrigerant. In the olden golden days, I would have looked for a malfunctioning heater hose valve or stuck door, but this doesn't seem to be that simple.

If I turn either side's temp up, the air comes out REALLY hot and if I turn it back down to 60 degrees it slowly goes back down to warm...slightly warmer than the present mid 90's here in south FL

So, it seems to be partially working, just not keeping all of the heater core heat out of the vents.

Tomorrow, I am going to see if I can track down a service manual.

Thanks

dknarnd · August 23, 2007

The reprogram of the AC that the dealer did changed the characteristics of my AC quite a bit even changed the temperature of the air compared to be about 3 degrees cooler; by this I mean if I used to set the temp. to 72 to be confortable now I set it to 75. Since I bought the truck used I don't know what it was like new but after the program the function of the entire automatic climate control was much better.