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Confused Comfort Controls


Charter Member
SM 2003
Full Member
Jan 28, 2002
Larkspur, CO
It happened again today. The heating and A/C controls took a crap and refused to cooperate.

In a nutshell, they "froze" me out... literally. The only control that minded was Mr. Fan. No matter what controls I pushed, all I got was cold morning air from the dashboard vents (and rear of console):

A/C wouldn't kick in
Outside/Recirc controls did nothing
Mode knob had no effect
Temperature knob had no effect

At the next red light. I shut off the engine, restarted and everything worked fine again. Weird eh?

Anyone else have experience this problem? I wasn't able to duplicate it again... should've driven straight to the dealer to let them have a look.
Do you have the "Climate Control" or just the heater and AC? I think I have heard rumbles about the Climate Control being flakey.
I have the same problem with my Climate Control. Even if I shut everything off I still get air coming out of the ducts. If the temperature knob is set to warm then warm air comes out. The same thing applies to the temperature knob when its set to cold. Keep in mind that it does this when I have EVERYTHING shut off.
Wierd I'd say. I insist that I just have not figured out how to use it yet. I am going to play with it this weekend. Usually everything with the Avalanche that I thought was wrong initially, either was error on my part or a rather cool feature.
Aha... so it's not just me, eh? I have that same problem as well; when EVERYTHING is shut off, I get a light draft of hot or cold air (depending on the position of the temperature knob) from the vents.

This morning's problem though, went way beyond that.
This is PoetryBo(I'm not signed in yet) I've had the same problems with air coming in through the vents even with everything shut off. I also have the climate control. I've found, however, that when everything is turned off AND the button to recirculate the air is pushed... air no longer flows in through the vents. I don't know if this is supposed to be the case or if it's a quick fix but that's what I've found ;)
I don't know how much air you have coming out. (This has nothing to do with the glitch). I'm pretty sure that even with everything off air will still come out. I think it says that in the owner's manual. Of course, if it's blasting you with cold air then you definitely have a problem. :rolleyes:
For those of us that have the Climate control, when you have the settings set to auto on both your fan and your location....the default would be air coming out of the defrost and by your feet.....you shouldn't have any air coming out of the vents directely in front of you.... :)
If I am not mistaken if the setting is Auto and Re-circulate you should not get any air at all. If the setting is for outside air then it's like fan mode..(even in the off mode you will get air circulating).. My Monte Carlo works the same way.
I had a simliliar problem with a 99 Silverado ext cab. If you want AC and all you get is hot air look at this first. If you can tell if the refrigeration compressor is running or see if the refrigeration suction line (the larger one to the air box) is sweating and cold. If so, then it is possible the damper motor and not the climate control. The service dept first changed my control box first. Before leaving I tried it and had the same problem.
To prevent CO poisioning....When the Climate controls are off air has to come in the cabin. So the outsided vent is opened and air is drawn in not forced by the fan.

This is normal for all vehicles. Where it comes in at probably depends on where you last had the air directional knob pointed too.
Not necessarily true, If mine is in the off position, I can hit the recirc button and the vents will close as long as the vent position dial is not on the floor or defrost vents. Like wise, I can hit fresh air button, and can fell air coming in while in motion. The button will flash a couple of times, and then the vent will stay in the open position.
timcosco . .

At last someone else who has experienced this! ?I posted a thread about two months ago with the EXACT same symptoms - with my manual controls - only the fan switch did anything - blew cold air out of the defroster. ? Shut it off, turned it back on - no problems - and no re-occurance of the problem since then either. ? Never took it to the dealer - it's hard to fix something that ain't broke!

This is one of the two items that I reported to Chevy on their quality report (the other was the tailgate falling open).

PS - most of the other discussion here is normal - with the fan off and outside air selected, you will get air out of the vents while moving. ?If recirculated air is selected (possible only with dash or both dash and floor vents selected) then little air comes out of the vents. ? The flashing light on the recirc button indicates an incompatible setting - i.e. floor vents selected. ?The combination of floor vents and recirc air doesn't make sense as the return air in the recir mode is right beside the floor vents - the system would sort of feed on itself, doing little cabin air circulation.

wrchism said:
I posted a thread about two months ago with the EXACT same symptoms - with my manual controls - only the fan switch did anything - blew cold air out of the defroster.
'Ya know, I thought so, but couldn't find the post; so I started another. Happened to me twice since December but I can't recreate it. Since we're both in CO, it must be an altitude thing, eh? ;)
wrchism - you have answered my wife's question! She keeps telling me that she sets the controls and the light flashes and I told her she's crazy. I finally realized that it has to do with incompatible settings, and you just answered why that is the case! Thanks for the info. :D
Is the rear window defrost supposed to come on automatically? Even without the rear window in? When it's 70 degrees outside, sunny and dry?
Is the rear window defrost supposed to come on automatically? Even without the rear window in? When it's 70 degrees outside, sunny and dry?

No . . . It only comes on when asked to - by pressing the button on the dash. Though, I don't think that the rear defogger has any idea a to whether the rear glass is in place - at least not given the warnings in the manual regarding installing / removing the glass with the rear defogger on . . . you get SPARKS!
wrchism said:
timcosco . .
If recirculated air is selected (possible only with dash or both dash and floor vents selected) then little air comes out of the vents. ? The flashing light on the recirc button indicates an incompatible setting - i.e. floor vents selected. ?

man, you just answered my major (but on a minor issue, aren't the most annoying issues this way) beef with my Avy cliamte controls - I often get behind school buses belching diesel smoke in the morning, and tried unsusccessfuly to go to a recirc setting so my blasting heat would not suddenly fill the cab with the exhaust - well you know I was unable to do so, and now I know it ain't broken, it is just a sh*tty ass design - but to answer all airflow questions - GM was waaaay sensitive to exhaust gases coming back into the cabin since it is possible that the Avy would be operated with the midgate down, rear window removed, and yes, even tho the OM says not to, with the rear gate down also. So I think they made it nearly impossible to avoid fresh, outside air coming in throught the vent system . . .
I have the auto climate controls and only when it is set to that position does the "skunk" button become usable, i.e. cut off outside air. When it is in any other position, I get the "flashing" no-go light when I try to use it.
Astro ventalation is what gm used to call the normal flow of air with all the contols set to off...as stated this is normal. :B:
Hey Boatnfool: My folks had a 1970 Chevy Kingswood Stationwagon with "astro ventalation" That was a big selling item back then. Fresh air with the windows up! Almost as good as air conditioning. Not. :2:
I found this service bulletin on a GM employee website this might help.

Loss of HVAC System Mode and/or Temperature Control (Reroute Wiring Harness) #01-01-39-007
Loss Of HVAC System Mode and/or Temperature Control (Reroute Wiring Harness)
1999-2002 Chevrolet and GMC C/K Pickup Models (Silverado and Sierra)

1999-2002 Chevrolet and GMC C/K Utility Models (Avalanche, Surburban, Tahoe, Yukon, Yukon XL, Denali)

2001 GMC Sierra C3

2002 GMC Sierra Denali

2002 Cadillac Escalade, Escalade EXT

Some customers may comment that they cannot control the HVAC system modes and/or the temperature. These concerns may be intermittent.

There may be poor terminal contact and/or bent terminals in connectors C206 (RPO C68 automatic HVAC controls) or C296 (RPO C60 manual HVAC controls). Excessive tension on the wires due to the wiring harness being misrouted in the instrument panel carrier may cause these conditions.

Remove the Air Bag fuse.
Disconnect the steering wheel and instrument panel (IP) air bag connectors. Refer to the SIR subsection of the Restraints section of the Service Manual for connector locations.
Remove the IP upper trim pad.
Locate connector C206 (6 cavities) or C296 (8 cavities). The connector is attached to a metal brace on the far right side of the IP carrier above the IP air distributor duct.
Inspect the routing of the wiring harness to the connector. The proper routing of the wiring harness is above the air distributor duct with no tension on the terminals in the connector. The routing is improper if the wiring harness is below the air distributor duct with excessive tension on the terminals in the connector. The excessive tension may cause poor terminal contact, resulting in open circuits, in the connector. The wires may also pull the terminals out of the connector or pull out of the terminal itself.
If the harness is routed properly, contact Technical Assistance for further information.
If the harness is misrouted, remove the connector from the brace.
Disconnect the connector.
Perform a pin drag test on the female terminals.
Inspect the male terminals for straightness.
Inspect the wire to terminal connection to insure that no wires have pulled out of the terminals.
Reroute the wiring harness above the air distributor duct.
Firmly reconnect and reseat the connector.
Reattach the connector to the metal brace.
Reinstall the IP upper trim pad.
Turn Off the ignition and reconnect the steering wheel and IP air bags.
Reinstall the Air Bag fuse.
Turn ON the ignition and verify that the air bag light flashes seven times and goes out.
Clear any diagnostic trouble codes that may have been set.
Verify proper operation of the HVAC system mode and temperature controls.
Warranty Information
For vehicles repaired under warranty, use:

Labor Operation
Labor Time

Panel, Instrument Panel Upper, Remove and Replace
0.7 hr

To Repair and/or Reposition Connector and Harness
0.3 hr

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information. WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

? Copyright General Motors Corporation. All Rights Reserved.
Thanks for the post Av3. I made a copy of the bulletin and handed it to the service manager when I took the AV in today for my intermittent A/C problem.

We'll see if they got it fixed soon I'm sure.
Thanks, Av3. I, too, took the TSB to the dealer this morning.

Is that GM website available to the general public?