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GMC Yukon AC and Heat Questions



  • artaqqartaqq Posts: 6
    I have a 2005 Sierra Denali that I put a new battery in last night. This morning when i started it, all seemed well except the A/C was blowing out full heat. I parked the truck and disconnected and reconnected the battery. The Air kicked on and started working, then turned back to full heat. It's a 25 minute drive to work so, i just shut the climate controls off and drove in with the windows down a little. When I parked at work, I tried it again and it initially was blowing heat, then the A/C kicked in and it was back to normal. I don't know what to expect when i leave but, was wondering if this has happened to anyone else?
  • bcrawfo2bcrawfo2 Posts: 8
    This really is insane.
    If the the sales sticker on our trucks said "If you ever have to disconnect the battery, you will need to re-calibrate your climate control. If you fail to do that, you will likely cause permanent damage to a device deep behind the dash.", none of us would've bought these vehicles.
    But...strangely...that's the symptom we all have.

    OK....rant off.
    Supposedly when the AC system loses power (battery change)....the actuators that control air flow thru the AC system need to re-calibrate themselves. They do this by "hunting" the range of their movement. Move to one extreme until they can't any further....remember this position. Then move to the other extreme and repeat the process. I think sometimes that happens ok, but if for some reason it doesn't...the system will remember a bad limit and keep trying to have the actuator reach that unattainable position. Do that for a long period of time, you do permanent damage to that actuator. Now....when that actuator needs to be replaced, you have a $400-$500 service bill which involves removing the whole dash.

    There are procedures involving pulling the fuses or discharging the computer and then re-applying power and letting the AC system figure it out...I just don't get why that doesn't work right in the first place.
  • alnahdialnahdi Posts: 1
    I have Yukon 2007 SLT when I start the car the A/C start immediately and the temp is 74F fan on low although I had switched off the ac before and I changed the temp and the display changed to centigrades can any help meow have the same problem
  • Hello i have a 2000 or 2001 gmc yukon 5.3 this issue started roughly on & off 2 winter's ago.

    I have been reading e-mails, but not seeing my issue as bad as mine.

    It started in the winter 2 years ago, on & off all season & now for the last year it is continually blowing out wrong air. I would turn on the heat, and it would blow hot air for like 30 seconds, then it would turn to ICE COLD air coming out, then the summer after that( last summer) when i turn on the a/c it blows out HOT HOT air( could burn my hand if i kept it up to the vent). now like i said, when it first started, it was on & off, but now for the last yr it hasnt stopped 1 time! also, in the summer because it sooooo hot outside, i have to put the vents on defrost so the hot air will blow out up there & not on me, but even with the whole system off, it is still blowing HOT HOT air on me. I have to keep my ALL my front vents closed & it still blows it on my feet continually while i am driving.

    any input would be great!
  • artaqqartaqq Posts: 6
    Hi, Danielle.

    You might want to replace the AC fuse and see if that helps. My fuses were all fine but, I took them out and put them back in and the problem went away, so far. Someone commented here and said that sometimes you have to reset the heating and cooling system by replacing or just unplugging and re-inserting the fuses. Anyway, it seemed to work in my case. I had also unhooked and re connected my battery, since replacing the old battery seemed to trigger the problem in the first place. Best of luck to you. That's an unbearable problem to have.

    Let me know how you come out.
  • I have 99 Yukon that has a problem with the front air. The back air works fine. It has a new control unit in the dash. Compressor is working fine. Cold air is not coming out of the front vents. Would also like to know if there is any way to look at a service diagrahm of what's under the dash. We have had this vehicle to the dealership twice for air problems. First they charged it up and ran fine for a little while, then they put in control unit, which they charged us alot for. I'd like to be able to fix this myself. Any help is greatly appreciated. Thank you!
  • Air conditioning was working great. Was freezing. We did have to replace the condesor and the o rings but its been working great! Came home from shore on monday and now neither the front or rear air is cold its luke warm . What could it be ?
  • houndshounds Posts: 1
    For the past 4 months my AC was working at Setting number 5 only; Just last week the front A/c stopped working and now only the rear one works. I bought a new AC Heater control and installed it and it still doesn't work. Can someone please help with some advice? :mad: :cry:
  • Same on my 2000 Tahoe. Have been told to replace control panel but don't want to spend $400 on a new one and can't find a used one $100 close to where I live. However I have managed to unplug existing panel and reconnect. Worked for a couple months and has stopped working again. Sometimes it will work if I give the panel a good hit with my palm. Previously have changed blower and all relays and resistors. All points to Control panel.
  • I have the same problem. My AC blows fine for a short while before blowing hot on the driver side, still cold on the passenger side.
  • Did this fix the issue permanently. My A/C functions normally on startup then switches to hot on the driver side only, after a few minutes. KMS
  • We all seem to have the same problem, hot air blowing out of one side, cold on other or just switches to hot period for no reason.
    I've concluded this loyal GMC / CHEV owner for 40 yrs is going to start a new loyality to FORD.
    Hundreds of questions yet not a single solution....My misery started with a dead battery. Charged it up and yes hot air only on drivers side when A/C is on, pass. cold.
    2005 Avalanche, 21,000 miles like new but only able to drive in northern ALASKA where the heat is on 24/7 365 days a year...who needs A/C up there... :mad:
  • foussfouss Posts: 2
    try turning unit off and disconnect the battery for a couple minutes .Then reconnect battery and try it out.My system drove me nuts for a year until I did this step.Good Luck
  • I really appreciate your reply on this frustrating issue. I turned climate control system off, turned off ignition and disconnected both battery terminals for 30 battery cables and started engine., Immediately felt cold air out of vents with A/C on but after about 20 seconds, hot air blasted drivers side and freezing cold air pass. side.
    Temp. set at 60 degrees yet hot air...
    I would think after disconnecting battery, I'd have to re-program my power set settings.
    Power settings were still remembered by computer so I guess I'll try the local dealer see if they can flash the unit back to factory settings? This all started by a dead battery...nuts :cry:
  • rainyday2rainyday2 Posts: 3
    edited August 2010
    Suddenly the heater in my 2002 Yukon will only produce heat when I flip the heat control switch to "max" detent position, then I get max heat. In any other heat setting the heater fan blows but no heat. The fan works fine, just no heat except in "max". Any ideas?
  • Your misery is felt by thousands of loyal GMC/Chev customers.
    Try disconnecting battery 10 minutes, remove HAVC A/C Heater Fuses.
    From what I've read, disconnecting power causes the computer to default back to factory setting.
    Its worked for many but not avalanche is off to dealership tomorrow unfortunately $$$$$$$ :lemon:
    Good luck...
  • harley2die4: Thanks, I'll give it a try and post if it works or not.
  • harley2 die4: Well it worked...sort of. I did just as you suggested and when I started the engine with the heat control at mid-range, I got heat. I then moved the control to full (82 degrees, not the max detent) and I got more heat. But then I moved the control back to mid-range and lost the heat. I tried the sequence again, waiting for 45 minutes before putting it back together but joy. Still have the original problem. The fan operates fine but the only heat I get is max heat in the "max" detent. Still open to suggestions.
  • I think different steps work for different models / year ..I own 2005 model Avalanche
    Start vehicle
    Immediately turn A/C off but climate system on.
    Turn vehicle OFF.
    Disconnect ( - ) negative battery cable
    Disconnect HVAC ( 10 amp fuse ) and both A/C fuses if youy have 2
    Wait 10 minutes.
    Start for minute, turn vehicle OFF.
    Install HVAC fuse only
    Start and run climate control settings taking time to listen for defrost, vent, floor cycles to work properly. See if heat is still coming out on low temp setting.
    If no heat, push recycle button you use when A/C is on sucking only cabin air...
    No heat hopefully...
    I spent about 5-8 minutes driving around the block doing this.
    Not sure if the vehicle needs to be out of park or driving to make this way work??
    ( I guess with parking brake on, in neutral might work also )
    What I've read, you need to re-calibrate the climate system with A/C off. Making sure all the settings are functional.
    Turn vehicle OFF
    Install A/C fuses.
    Start car A/C OFF......
    Keep A/C off
    Run climate settings again on cold detecting any heat ??
    Hopefully not...
    Push A/C button ON
    Hopefully this will solve your problem.
    After 2 days of reading comments, this combination worked for me.
    This should be a recall issue...
    Good luck
  • artaqqartaqq Posts: 6
    We all do seem to be having the same problem and I don't want to imply that it's no biggie but, jump to Ford? Bah, Ha!!! If my truck is 150 degrees in the cabin, I still know I have the horse power, transmission, durability, dependability and safety I need. In your Ford at 80,000 miles, you'll be replacing a transmission, probably your fuel pump and more than likely your rotors. You will have struggled through 6 months of fuel system headaches...if you're lucky...resulting in a $600 - $1000.00 computer replacement. Buy a Dodge and you better buy a Gas Station and a Transmission shop. I always say, 'People who drive Dodges just hate money. People who drive Dodges and own Horses REALLY hate money!'

    I hate the fact that the Government owns 'GM' and all of the crap that goes along with it. They should have just been allowed to fail, filed for bankruptcy, restructured and stayed out of this Government's debt. My last two GM trucks had over 230K miles on them and never had a major problem until they had over 150K miles on them. Then it was a Transmission both times.

    I won't be leaving GM until they pry the keys of my bloody, lifeless hand. I say, reconnect your battery a couple of times if necessary and be glad the biggest problem you have is a Heat issue. Think of our less fortunate Brothers and Sisters, in their Fords and Dodges, sitting on the side of the road in 115 degree heat and no way to drive out of it. :)
  • $55,000 for my GMC, I guess expecting cold air when we push A/C and getting 90 degree blast of hot air would cause the average hard working American a bit pissed, especially finding out it was caused by something as simple as a dead battery.
    Disconnecting the battery cables does not fix the problem.
    Myself, I'll be buying FORD 350 next...I called GM, they never returned my call....
    I'd call Obama but he is always on vacation....
    Mybe if I drove it to Arizona border, left keys in it, illegals could drive in style..
    just a thought
  • trex354trex354 Posts: 1
    Hello. Well, I hate beating a dead horse on some things...but every opinion is worth a try.

    I am lead to believe that since your vehicle has dual climate controls, you MUST have TWO mixer doors, one for the drivers side and one for the passenger side. It seems to me that the mixer door for the driver's side needs to be be replaced........I hope this works.
    Keep kool.....
    Bill from NJ
  • Your thought is common conclusion had the battery not been dead, however, once the battery is charged start vehicle, the A/C works perfect for about 20 seconds, then hot air blowing drivers, cold pass. side.
    Replacing mixer doors at a cost of $1,400 would not solve the problem.
    Owners need to re-program the climate control system which I did successfully.
    Disconnect A/C & HVAC fuses.
    Start and run for about 30 seconds, turn off.
    Install HVAC Fuse only. ( A/C fuses leave disconnected )
    Start and while driving turn on climate cold setting and run through the different controls, foot, vent, defrost etc. making sure the system is working properly several times.
    Turn vehicle off...
    Start and re-do sequence several times.
    Turn vehicle off.
    Install A/C Fuse
    Start while driving turn climate control on with A/C...
    These steps resolved the problem, re-calibrating climate control systems memory.
    Again, this should be a recall issue and thousands of loyal GMC customers are being charged $1,400 or more from dealers.
  • svigilsvigil Posts: 5
    DO you have a diagram and part number for this. I was about to replace one of the door actuators however nobody has been able to tell me which one to replace. I need the Driver side
  • danial2danial2 Posts: 2
    2001 Yukon XL 1500 Front heat & air fine, rear ac blows hot as if heater is on in all settings. As if air is going through heater core instead of ac. What to do?
  • danial2danial2 Posts: 2
    FYI for others. I had read other comments. Disconnecting battery for over 10 minutes, connecting battery fixed my problem.

    Thanks to all,

  • Your situation might be different than mine. My problem began with a dead batter screwing up memory of the climate control unit.
    read a few posts back the steps I wrote to clear control system.
    if that does not work, you might have a faulty HVAC door that needs replaced.
    if you can't find my post few days back, I'll list them again.
    GMC misery :mad:
  • My battery just went dead and I unhooked it to charge. After hooking back up, my Automatic Climate control system does not work correctly. It will only direct air through the defrost vents and not to the front vents in the dash What causes this and is there an easy fix?
  • artaqqartaqq Posts: 6
    Just try reconnecting the battery. There's something goofy that happens when you mess with the battery but, by disconnecting it and re-connecting it, the problem seems to go away. I have seen some comments about unplugging the A/C Fuse and plugging it back in, to reset the system. The comments and suggestions have been all over the favorite was, 'I'm switching to Ford!' He thinks he has problems now...Heh!

    Hope that helps! It worked for me but, not for others. But, it's all I got.
    Best regards.
  • I had the same problem after a dead battery.
    For a few owners, disconnecting battery for 30 min. reconnect resolved the issue. The majority of us, it doesn't.
    Further discussion with a GM mechanic, climate control system needs to be reprogrammed. Read back a few posts you'll see what worked for many of us that I posted.
    Disconnecting the battery, computer climate control still keeps memory.
    If you have power seats memory button for driver 1 & 2, you'll find seat memory is not lost when battery disconnected, same issue with climate control.
    This should be a recall issue.
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