One side of A/C blows hot

[Blue Tank]

This is the perfect compliment to the drivers seat heater that works unless it's really cold out.
'04 burb with the automatic climate control and good readings on the high and low side. Last year when it was really hot out the drivers side upper vents would go in to super hot mode occasionally. Typically this would happen on a very hot day, 85-90+. This year it's much more common and happens while the pass and rear vents blow cold. If you turn the hvac control off and then back on in a minute it will go hot again. If you come to a stop and turn the truck off and then fire it right back up it will normally blow cold for a while. I'm thinking it's probably one of the inside temp sensors, upper or lower, but wanted to see if somebody ran in to this before.

[edhtrd71]

Hey, it's super common for those act temp actuators to go bad. The driver side is the easier one to replace. It is mounted on the underside of the dash very close to the middle. Takes a few 5.5mm bolts to remove. Btw when you buy a new one don't go plugging in the new one without it being mounted to test it out. They have to learn their stops the first time they are plugged in. I have seen guys grab one after another from the parts department because they kept plugging them in before mounting them. They would watch them work one time over and over. Super easy job.

[greasemonkey]

There is also a relearn procedure for the actuators, opinions seem to differ slightly on how to do it so you may want to do some research on it. If you don't have the calibration tool you can do it by pulling the battery cable or the HVAC fuse under hood for a bit. Reconnect everything, turn truck on and let the AC calibrate itself. With the automatic AC you shouldn't have to worry about the settings, it should default to 75 degrees when plugged back in.
I have had terrible luck with ACDelco actuators. I bought a Dorman the last time the ACDelco actuator started buzzing but haven't installed it yet so I can't say anything for the quality difference.

[greasemonkey]

I should add that you can try the relearn procedure before buying a new actuator; but in my case, all it did was make the actuator go full hot and I ended up buying a new one anyway.

[Blue Tank]

Thanks guys, that makes sense. Talking to the Wife she remembers both fronts going hot last year. I think I killed the battery a couple of times last year listening to the radio while working longer than the 10 minutes it stays on. Wish it had an Acc position like the '72.
What that makes me think is that I might have screwed up the flapper calibration and it's between states. I think i'll try to re-cal like Grease monkey said on the outside chance that will do it. I've had pretty good luck with Dorman stuff so i'll try them if need be. I'll post what I find.
Thanks Again.

[greasemonkey]

http://sparkys-answers.com/2011/08/h...procedure.html

I had to dig to find the procedure but this is the one I went by.

[Blue Tank]

I've been waiting on my reply in case the problem returned. Knock on wood, not yet. I couldn't get the thread on here to come up that I found in a search before. In the thread one of the guys wrote in to check your coolant level. I did and it was a bit low as usual so I topped it off. Hasn't blown hot since. Knock on wood again.
I'll update this as it goes along and let you know either way. Thanks for the replies.

[LBJ]

On my 04 Silverado, with manual Left/Right Temp Control levers, I have a problem I had on my 1991 GMC where the Heater door opened while I was using the A/C - it then blew full hot. On the GMC this door was controlled by a little motor that I changed out. It was tough getting to it but I managed. Now, these GMC parts made little clicking noises when they were going bad.

On the 04 Silverado, nothing makes any noise, the heater door just opens and I get FULL HOT AIR. I don't have a service manual for this truck. Are there some general pics for location of these actuator demons?

I may try the relearn procedure. I have found that if the door opens, all I can do is pull over, shut off the ignition, wait 5 minutes, and start up again. This has always fixed the problem, but is kind of a pain.

[greasemonkey]

LBJ, assuming you are having problems with the driver side air:

http://sparkys-answers.com/2009/09/2...s-hot-air.html

My '05 base model with manual dual zone AC will randomly blow full hot and only reset if the truck is turned off and back on. I have heard that you can take the actuator out, open it up, clean all the contacts inside and regrease it as they become sticky over time, lose contact, and start behaving abnormally. I haven't spent the time to do so, but I think if it isn't "buzzing" or clicking, you may have a shot at it working. In the case of my Tahoe, the actuators start buzzing loudly when the tiny plastic gears begin stripping out. I still haven't tried out my Dorman replacement to see if it works better than the Delco I had been buying. At least it isn't the passenger side, since apparently it is very labor intensive to change.

[LBJ]

Thanks GreaseMonkey. I cannot tell which side is malfunctioning. But, that's a good photo log of where to go in the dash. It looks easier than the 1991 GMC Sierra. That was a totally blind fix - I had to feel my way to the part, get it removed, and then replaced. I'll try a reset procedure first. Thing is, this happens at random moments. It is getting more frequent too. It always resets itself by shutting off the engine and letting it sit for 5 minutes. LBJ
**********
I gave it a relearn today. We'll see if it goes bad next time or two or three I drive it. Working fine right now, but that's the way it always begins.

[LBJ]

Hi Grease monkey, I have discovered it's the driver side that is not working properly. Thing is, it will reset and work properly if you pull over, turn off the ignition, wait five minutes, and restart. On the link you gave it says this may just be dirty pins. I may try this first to see if it corrects the problem. It strikes at random times, you can never predict when it will just start blowing hot air. The new part is $115 at Rock Auto so I'd need to try to fix the existing part first. I have a 5% discount code if I need to use it at Rock Auto.

[greasemonkey]

It may be worth it to pop open and clean the contacts, I still need to do that with my '05. It very occasionally will go full hot if I try to crack it off of full cold (rare around here in the summer). I did put the Dorman actuator in my Tahoe a while back, and it has worked great. Not a single noise, buzz, or tick from it.

[LBJ]

I think I'll just buy the new part and do the job once! Ha.

[LBJ]

Bought the new actuator from Rock Auto and it came today. Installed it. Then plugged it in like the above post says. Seems to be working fine. So far so good. Have about 2 plus hours driving to do soon so that should give it a good test. I bought the Dorman actuator, $40 less expensive. Thanks for the tips, all.

[68Gold/white]

Sooo, if you hear clicking, or maybe any noise, it may be stripped plastic gears???

[LBJ]

68gold/white, Based on what I have had happen on my previous 91 GMC, clicking means your actuator is stripped out. With my 2004 Chevy, no noises, just a blast of hot air all the sudden on the driver's side. On my 77 Chevy, some of the doors are controlled with vacuum lines. Those had broken down and had to be replaced - heck to get to. There is also a "HOT/COLD" mechanical lever that controls overall temp that can be adjusted under the dash to make it shut completely, as required.

[68Gold/white]

Thanks!
I bought this pickup from my good friend in August. THe AC blew ice cold.
The heat has been intermittent...I will check all this out.
I noticed a clicking noise from time to time, coming from heat/AC controller...

I checked with HO Reillys about the control head. The O.E. replacement is no longer available, it was around $100.00 the replacement is the unit that had factory rear window defogger, has a plug over the rear defogger button, if not needed. It's around $200.00
I've only just begun this ordeal...oh well at least it's not a ford or dodge

[LBJ]

Check with Rock Auto online. They have several tiers of parts and the prices vary. AC Delco is the most expensive, but they have Dorman and others that are less pricey. I used the Dorman part and it works fine.