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Chevy Silverado and GMC Sierra Climate Control



  • when my truck is warm and the controller has not been on cold the whole time it blows hot. only in summer. if knob is moved to warm in mornings, ac blows warm as soon as truck is started. any help would be appreciated. thanks in advance!!
  • duncanm2duncanm2 Posts: 2
    My 2004 Sierra fan switch was erratic then failed completely, fuse was ok. I removed the heater control panel and the back of the switch was melted. The fan was ok but seemed to be slightly stiff when spun by hand, so I replaced the motor and the fan control switch and everything is fine. My 91 GMC had a dashboard fire caused by a melted connector in the heater fan circuit. Why can't GM build a heater control that won't meltdown? Thicker wire or better fuses? Something other than nuclear meltdown of controls or resistor boards?
  • greg94greg94 Posts: 4
    same with our 2006 sierra.....
  • robinhood8robinhood8 Posts: 2
  • robinhood8robinhood8 Posts: 2
    If you have a Bumping noise around the heater blower, like I did ,then maybe this will help you.
    My bumping noise occured when you turned on the ignition to start or auxillary and also when you turned off the ignition. It would last for maybe 30 seconds or so. Now, I have seen people asking for instructions about how to remove the dash and all the work that that involves.

    OK here was my solution:
    By looking and feeling under the dash at the heater I could pretty much feel where the noise was coming from. It was right at a little vent door under the heater. (maybe, it is called a blend door) Anyway I found that when It was making this bumping noise that if I pushed up on the door on the unhinged side the noise stopped. So I thought, why not try to just block it open with something and see if that would stop the bumping. I had a little length of about 1/2 in. gas line left from another project. I cut off a piece about an inch & a half long and wedged it in between the door and where it seated itself. WaLa, no more noise.
    I don't guarantee it will work for your problem but it worked for me, and so far everthing seems to work perfectly normal with the heater. So it saved me pulling the dash as suggested by many blogs that I have read in either work or the cost to take it to a shop. If you have the same problem maybe it will work for you. If it works you can send me the $600. or so that people have said it costs to fix. I"m kidding. To tell you the truth it took longer to write this blog than to fix the problem.

    disclaimer: I don't guarantee that it doesn't cause a problem but I havn't had any problem myself.
  • damatt18damatt18 Posts: 1
    I have a 2005 Chevy Silverado 1500v6. Imagine the climate control dash set all the way down to cool and a rapid popping noise occurring. The noise is similar to gulping a drink very rapidly. The sound occurrs whether the air conditioning is on or off, or no matter if the blower is off or on high. What is this and how to fix it??????
  • mine does that only on certain level settings. If I recirculate inside air the level area can only work with say, the mid level or floor level. Some combos don't work. You may know this but just wanted to offer some help in case.
  • charlie107charlie107 Posts: 1
    edited June 2010
    Temperature control not working. Hot air constantly coming into cab--cannot shut off--. even though the controls are shut off or put in air condition mode. I tried overriding the blend door acuator switch and manually moving the flap with the truck running, but the heater core under dash still stayed hot. Is there some type of switch out on the firewall that prevents the hot water coming into the cab to the heater core; or could it simply be the control temp. switches on the control panel? Does anyone have a solution? Thanks.
  • clovelesscloveless Posts: 5
    As a last resort to be able to survive the heat for a while, I put a valve in the hot line from the radiator to the heater coil. It's on the right side of the engine and you can see it going into the heater coil. I bought one from a local parts house. Shut if off and it insures no heat reaches the heater coil.
  • dowelldrdowelldr Posts: 1
    This is a year late, but I have the same problem with my 1997 Silverado. I just spoke with my mechanic and I like his explanation. He says that the problem is caused by slightly low freon or possibly running the system on Max A/C for too long. The issue occurs when the core freezes up, or water ices over the ports preventing the cooled air from escaping into the vents from the core. When you turn the A/C off, the core has time to warm up, so the ice melts and the problem disappears...until you turn the A?C back on and it freezes over again. I'm not sure how low freon contributes to this, but his theory sounds plausible to me. To prevent the core from freezing, try not using Max A/C after the truck has run for a bit. Also, try turning the temperature to a warmer (less cool) setting to prevent the icing in the first place. I haven't tried this yet, but I'm hoping it will fix the problem until I can get my truck to the shop to check the freon levels.
  • stretch87stretch87 Posts: 2
    edited June 2010
    Hqave 2000 Z-71 extended cab,221,000 miles ! I still love this truck ,runs,rides fantastic still!!!! I Recently replaced battery, & have since had no A/C!! My mechanic & I tested all circuits,fuses,switches. charge.Etc. ALL seems well!!!! Went to dealer to have computer "RELEARN" how to turn on A/C!! They said blah blah blah BS... All worked fine till battery replacement,now ????????? Do not trust dealers to do right thing ,especially since my mechanic is an A+++ !! Also not really looking to drop few hundred $$$$ for &%^#^^% dealer to make-up solution!!! ANY IDEAS???? :mad: :cry: BTW A/C worked fine day of replacement,stopped working after!!
  • 04 Sierra climate fan control works on #2 and up fan speed, but not on 0 or 1, but will work when truck accelerates. Any tips?
  • dbbarretdbbarret Posts: 3
    I have same problem in 2005 GMC Sierra 1500. Used to only work at 2 and up (for a few months) but now it only works at 3 and up!!! Any ideas?
  • obyoneobyone Posts: 8,054
    You can find a replacement controller for cheap on ebay.
  • dbbarretdbbarret Posts: 3
    What exactly is the part called?
  • obyoneobyone Posts: 8,054
    You can find it here:

    Enter year make model
    under hvac---> controls-->dash control unit.

    You will have four selections. To be sure you order the correct one you will need to email them with your vin prior to ordering.

    Or you could have yours rebuilt here:


    I couldn't find any listing for a used replacement unit at this time. You could search ebay for GMC HVAC controller.
  • dbbarretdbbarret Posts: 3
    Thanks for your help - I emailed them with my VIN. Is installation pretty straightforward? plug and play?
  • obyoneobyone Posts: 8,054
    Yes plug and play
  • Got out of the truck yesterday and the vent fan just came on ...keys in hand. Turned off ac and fan but it came back on. any ideas why this is happening.
    Could there be a short somewhere.

    Thanks, steve
  • di you ever find a fix for your ac problems. i just bought an 2004 gmc sierra and its blowing hot out of the driver side, any info would help thanks
  • We ended up having to have the control module replaced. They also had to replace an actuator. I think it ran about $1,000.
  • 97bruin97bruin Posts: 1
    I have a 2006 GMC sierra 2500 extended cab 4x4. My problem is this; no air is being blown out of the fan when i turn on either my AC or my heater. I can turn the dial completely up to 5 and nothing comes out. It will slowly blow out cooler air (when set on AC) and increases as we speed up on road and will stop when we stop. Same can be said for the heater. Got winter right around the corner so trying to get this fixed asap (3 kids) and without spending too much. Any suggestions? Any and all helps/tips are appreciated!
  • obyoneobyone Posts: 8,054
    You will either need to replace the diodes that control the fan speed or replace the control unit with the latter being easier of the two.
  • if you found the problem please let me know what you did because my 95 has done the same thing. thanks
  • azekissazekiss Posts: 5
    edited September 2010
    I have a 2010 1500 and just withing the last few weeks the vents change settings all by themselves. I will have the A/C running thru the main vents and the it will change to the the defrost vents without me touching a thing, I then have to move the selector to the defrost setting then back to regular to get the thing nlowing right again. It is a intermitenet problem and I am taking it in on Friday, anyone have any ideas on this?
  • I have the Chevy hot air problem.If I select hot air I can't get cold air again unless I shut the system down for 10 minutes.What should I look at first? x
  • I have a 96 gmc sierra. The blower has 4 settings. Worked only on 3 and 4. Replaced resistors and relay. Now it works on 1, 3 and 4. What should I try next?
  • Replaced blower motor today. No change
  • I replaced the pigtail on the wiring harness and it fixed my '05. Have you tested the pins to make sure you are getting voltage @ the pigtail on each setting? That's were I would have started. If you don't have voltage at the pins through the switch setting range, then you have a bad switch, unless you can see where any of the contacts in the pigtail are melted or blackened. If they are the pigtail is bad
  • Thanks for the help. I replaced the dash switch tonight and that fixed it. Thanks again.
  • hi guys, i have a 2004 2500 with a 6.0. i turned my heat on yesterday and hot air only comes out the right side, everything else seems to be working fine, it blows just no hot air on drivers side. any suggestions?
  • Not quite the same A/C problem others are having. On start up, blows cold air fine but in a few seconds drivers side vents blow hot air. Disconnecting batteries for a spell no fix. Can anybody tell me where the controller and mixing door are located?
  • tbroadtbroad Posts: 1
    When I move the levers, the air coming out always blows cool for both the driver and passenger sides. Truck has 112,000 miles. Any ideas on what may be the cause. Problem just started this week.
  • xchrisxchris Posts: 1
    Did you find a fix for the (90 degree or ac) problem? My 03 2500hd is doing the same thing. There is great heat on the 90 setting, but on 89 or below all you get cold air.
  • Drivers side would not stay on cold air with A/C on. Would switch to hot air after a minute or 2. This is a dual system. Took out the actuator P/N 52402588 and opened it up. All the gears were in good shape but there are 2 phosphor bronze semicircular wipers under the final gear which I believe send the feedback signal. They had lost there spring action to some extent and the surface they wipe on was somewhat dirty. Cleaned both, bent the wipers a little more and lightly relubed the gears. Set the actuator in mid position along with the door. (just barely reach it as it protrudes almost to the right side of the floor hump) re installed it and it has been functioning like it should for 3 days now.
  • I have a 2002 Silverado and a few days ago I found that my driver side heat wasn't working. The truck has dual heat control (driver and passanger side). When I turn the heat ON to max for both, passanger side blows hot, driver side blows cold. Air does come through both sides just that driver side blown cold.

    What could be the issue?
  • I read you post on replacing the wiring harness which fixed your '05. I have a 2004 Sierra and the wiring harness has definite issues where it hooks into the blower under the passenger/glove compartment area. Some of the connections are burnt and it finally stopped working all together.

    Can I get just the part of the harness I need, or do I have to cut it out of a used truck at a salvage yard and splice it?
  • 03sierra03sierra Posts: 2
    edited December 2010
    I recently purchased a 2003 Sierra, and when I turn the heater on (anything past floor) the recirculation button goes off. The only way that I can get it to stay on is to keep the selector one space to the left of floor (vent/floor blend). Is this a design flaw? Did some engineer not realize that everyone doesn't park their truck in a heated garage and the 10 degree outside air is cold when it's coming in?
    Also-Besides adding an aftermarket kill switch for the A/C compressor when the selector goes into the Floor/defrost blend, is there any way of making it not come on? I understand the reason for it, to dry the air, but sometimes all you need is a little bit of heat to clear the windows, without having to use extra gas to run the A/C.
    Please let me know if there's a fix for this, as well as a fix for the defroster-A/C issue
  • I have a 06 chevy 2500 and been fighting with heater issues. I bought the pickup from dealer ship and said it been thru the shop and good to go! Since then i brought it home and heater works sometimes. I thought the blend door motor wasn't working so bought one and put it on and it worked for a while and now the heater still blows warm/cold air. I have noticed that then light on the dual climate control does not work when turn lights on, and wondering if thats my problem.

    But i get out and check the heater core hoses and one is hot and other is cold, so i drained the antifreeze and flushed system out and seemed to be dirty coming out of heater core.. Put all back together and worked for a week and a half and now i am back to same problem... As i messed with it more i have noticed that once i rev the engine up to bout 3500-4000 rpm the heater gets hot and then let off and goes back to blowing warm/cool air.... so i wonder if water pump is weak???

    i am at a lose and wondering what to do next! anyone have any suggestions???
  • obyoneobyone Posts: 8,054
    You need to back flush the motor and heater core. If you don't have the attachment or the compressor to do it you may have to take it to a shop to do. Sounds like you may have found the problem with the heater core being clogged. The other thing to make sure of is that the coolant is topped off.
  • i am having the same issue with my 2004 2500hd sierra. did you ever figure out what the problem was?
  • I was wondering this also so I did a good google search and this post popped up. After a few days of searching I figured it out. The answer is No... The "manual" HVAC control has 2 electrical plugs on the back while the "auto" climate control has only one. I'm sure that with the proper schematics and maybe a different BCM that this could be done but not just a simple swap. I wish that it was an easy swap because the auto climate control simply looks better to me. Oh well... Hope this info helps anyone interested.
  • I have a 1979 gmc k1500 v8. i put a radio in and my heater keeps shorting out or the radio will its ramdomly doin it. i thought the wires were crossed but iv takn the dash off and checkd the wires with a meter.. i cant figure out whats wrong with it and am geting very frustrated considering its snowing and cold..any1 have ne ideas?
  • One thru four Heater fan speeds work, but #5 the air flows stops. Anyone have this issue and does anyone know the fix?
  • furrowjockyfurrowjocky north central MontanaPosts: 13
    pickup has 600 mi on it. the button on dash that says passsenger I assume shuts off heat to passsenger side. It does nothing, I have no floor heat on that side but do have defrost. Also button for circulating inside air does nothing. the ouside air button stays lit all the time. Is this a problem with 2011 sierra's?
  • furrowjockyfurrowjocky north central MontanaPosts: 13
    edited February 2011
    I'm replacing my 06 sierra 1500 crew with a 2011 sierra 1500 crew. I'm in Montana with below zero temps this winter and my new sierra has heat circulation problem next to the doors. The vents that are directed towards doors have a shortage of air coming out of them, compared to the center ones. Service manager is willing to check and make sure air deflectors are working properly, but thats about it. I may have to plug center ones to get results if he can't find anything wrong. Any one with same problem? Also it won't recirculate cabin air in heat mode, is that normal? Another owner on another form says his does. Any ideas on these problems would be greatly appreciated. Thanks
  • gmcustsvcgmcustsvc Posts: 4,252
    Have you been back to the dealer to address your concerns? If not I would definitely recommend doing that first. Please keep me updated on your situation.
    GM Customer Service
  • slagrimslagrim Posts: 1
    once heat control is switched to hot it will not switch back to cool unless engine is switched off and not restarted for @15mins and the controler has to be on cool before starting the truck. If the A/C is being used and the controler is moved to adjust the temp it will go to heat and not return until truck is turned off and restarted with switch in cool position.
  • dslovedslove Posts: 1
    I have same problem. It might be the resistor in the air box behind the glove box. I have lights out on climate control panel. Any one know what type and size they are?
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