GMC Yukon AC and Heat Questions

lpfeiferlpfeifer Member Posts: 8
My front fan quit. Last December, I got a new front control, installed it and it didn't help. I removed the resistor block, cleaned it and spun the fan and it started again. Now, 6 months later it quit again. I did the same thing as before and it ran for a couple of days. This time it started again on its own for a short time, but the rear air fan also quit once. Would it be the body computer?? I know I read something about the noise coming from the headliner, the auto temp sensor fan making noise, it is or has in the past. Also, wondering about a dead spot on the armeture, but it doesn't explain the rear problem too????
Thanks for any help, Lyle Pfeifer


  • faucettfaucett Member Posts: 1
    I have the same problem in my 2003 Suburban. Has anyone any ideas?
  • lpfeiferlpfeifer Member Posts: 8
    I tracked it down to the wires that go from the fan motor to the resistor block. If you remove the plastic cover on the bottom of the fan unit, mine has 3 screws in it, one is just about the middle of the tunnel. The resistor block has 4 wires in and 2 out to the fan motor, the resistor block is about 2.5 inches by 2 inches and held in with 2 screws about 8 inches from the passenger side wall. Also, while you are there, you should probably change the central air filter, mine was really dirty. If I tap on the block or move the wires around, it will start up again. I need to trace the wires out and see if they are bad or the connector to the resistor block. Hope this helps you. I think the plastic cover pushes the wires up to tight and bends them to the point of breaking the wires or the connector to the block.
    Lyle Pfeifer
  • ccryderccryder Member Posts: 2
    On my 2000 Yukon the carpet on the passenger side is wet all the way to the back seat. I think it is the ac drain stopped up. Not engine water, no antifreeze.
    I have crawled under it but cant find it.
  • edfresh2edfresh2 Member Posts: 1
    I just got a 2001 Yukon XL with the same pblm. Did you ever get this fixed? I still have the warrenty so I WILL eventually get it fixed. Thx - Ed F.
  • ccryderccryder Member Posts: 2
    It is in the back on the right. Behind the right rear wheel. THe one for the front is inside the right front wheel. Been a while now but I finally carried mine to a mechanic. THey had to take the cover off inside the car; to the right of the rear seats to get to it to unstop it. My front one was ok.
    My problem was that I didn't know there were 2; one for the rear and one for the front. I thought everything worked from the front but there 2 complete systems, only one compressor tho.
  • ge_ccoge_cco Member Posts: 6
    I have a 2001 Suburban with auto climate control. It started acting differently at the end of summer . . . everything still works the same as normal, except that when the cabin temperature gets to where it should be, the system doesn't back off enough. The computer still controls the fan speed, directs the air to different vents, and blows hot or cold air as required. Now in winter, it eventually gets too hot in the car, but it's still blowing hot air. I turn the temperature control down to minimum and adjust the fan speed manually to the lowest setting, but the air temperature is too hot and the car keeps getting warmer. Same in summer - it would keep blowing cold air, and with the temperature control set to 82 and the fan on minimum, it still got colder in the car.
    The thing is it's different from how it used to work, where it would control to the temperature that was set.
    The dealer simply said that I need a new computer. But to me it seems like a sensor problem, because the computer is still doing everything that it normally does, except backing off when it reaches temperature. It's as if it can no longer sense the cabin temperature correctly.
    Has anyone had any problem like this, and if so did you figure out how to fix it? Any thoughts would be appreciated.
  • lpfeiferlpfeifer Member Posts: 8
    I believe if you look above your head and to the left while seated in the drivers seat, you will see a round plastic grill, about the size of a quarter. This should be your auto sensor. There is a fan in it that should have been making some noise for some time, almost like a sound over you speaker from the engine. I know I saw something on here about the part number and color code of this unit. I belive its about $25.00. Someone here took his out and cleaned and lubed it.
    Update on my problem, it started again, not to work. I pulled the controller out and the plastic was somewhat melted again. It looks like the meatal tab that is suppose to come down hard and make good contact on the controler contacts was hanging up in the plug, creating a lot of resistance, causing the thing to heat at the contact point. I worked the metal contact down so it makes good contact, but the wires are now somewhat hard from the heat. Looks to have been a defective plug from the factory as I have never had this part out since new.
    Good luck, Lyle
  • joesdenalijoesdenali Member Posts: 1
    I have a 2004 Denali that blows heat and A/C through the defrosters only. The dealer has "adjusted" some sensor three times based on the TSB recommendations. What should I do??
  • beubeu Member Posts: 4
    Probably a vacuum leak to the vacuum controls of the HVAC if it has vacuum controls instead of electrical. The defroster is the default if there is no vacuum. Does it idle rough?
  • duke5259duke5259 Member Posts: 1
    I have this same problem and I do have a bit of a rough idle. Any ideas where to start troubleshooting the vacuum system?
  • cheapengineercheapengineer Member Posts: 36
    The A/C in my 2004 Yukon XL wasn't getting cold any more. I figured it was a basic freon leak. Dealer said the control module needed to be re-programmed. Charged me 2.5 hours labor at 95 $/hr. They could not explain what went wrong or why it needed to be reprogrammed, they just said that is what needed to be done.

    Did I get duped?
  • jlflemmonsjlflemmons Member Posts: 2,242
    Ouch. I had the A/C computer go wacky after changing the battery in the '04 this past weekend. Passengers side front blew cold, rear blew cold, drivers side hot. Dealer offered to 'reprogram' system.

    Well, I work with computers every day, and I know that unit must have a "self-learn" function. So, I went to the fuse box under the hood, pulled the fuse to the A/C control system. Waited a few minutes, reinstalled the fuse, and started the car, and within one minute the system reset and started working correctly.
  • motrcop2000motrcop2000 Member Posts: 2
    I put a new condenser, front and rear dryer, evaporator, and compressor on the A/C and had the system charged. Besides being a pain in the butt of a job, the rear A/C fan no longer kicks on. I checked the large gray fuse and small 10amp fuse under the hood and both are good. I have tried kicking on the system by pulling the fuse, waiting, and then replacing and got nothing. I tried to turn it on using the auto button front A/C control, rear A/C control and rear A/C auto and I get no air at all you can't even hear the fan kick on. The front A/C works great, never better. WHAT AM I MISSING?
  • jlflemmonsjlflemmons Member Posts: 2,242
    Are you getting voltage to the rear fan?
  • motrcop2000motrcop2000 Member Posts: 2
    I got what your saying. The rear fan motor could have a short or could need replacement. I feel kind of stupid now. So where might I find the rear fan motor to test it? Is it in the headliner and if so where at?
  • jlflemmonsjlflemmons Member Posts: 2,242
    I don't know for sure, but usually a rear cooling fan is mounted near the rear evaporator, like drivers side in the rear quarter? It is easy to move air through the plenum to the vents, not so easy to find a place for the fan motor.
  • lousyaclousyac Member Posts: 1
    I've got a 1997 GMC Yukon (bought in 2001). Anyways, it's always had this problem: the fan starts blowing, I can feel the faintest leak of hot or cold air out of the vents, but no air comes out of the vents. This is an intermittent problem. Sometimes it works fine, sometimes it doesn't. No telling when it will fail or when it will work.

    Of course, over multiple trips to the mechanic it has worked every single time for them.

    This is driving me nuts! At this point, if there's a part that's a likely culprit I'll just buy it, hand it to the mechanic and have him replace the !#[email protected] thing. Does anybody have any ideas what could be failing that would keep that nice cool (or hot) air from getting all the way into the cabin ?

    Thanks in advance,

  • kuzkuzkuzkuz Member Posts: 2
    Hey guys...I have a slightly different problem on my 03 Denali, and wanted your input.

    When I turn on the AC, the motor is actually making a sound. It sounds like something might be caught in it, but it's a humming sound, and I don't know how to go about diagnosing it.

    Also, there is a clicking sound, but ONLY when it's on the direct ahead placement. Whenever air is directed to my feet or the defroster, the sound goes away. I'm sure a dealer will scerw me, so I wanted your input. Thanks!
  • jrookingjrooking Member Posts: 1
    Hey Guys..I have a problem with the a/c unit on my 2001 Yukon xl.

    I change out the a/c belt and the belt tensioner becouse they were worn out.When i turn on a/c all was good while at adl,but when i accelerate the belt tensioner would jump,bounce,and make a clamping noise.

    Just don't know what to cheak for now,any ideas were to start trouleshooting next or what to look for?
  • jlflemmonsjlflemmons Member Posts: 2,242
    Sounds like the belt may be defective. If the belt has a hard or soft spot, it will flex at different rates as it goes around the pulleys. At idle it isn't so noticeable, but at speed under load, it can really make the tension pulley jump.
  • fred_pghfred_pgh Member Posts: 1
    I have an 02 Yukon with a host of heating and A/C problems. I don't know if they're related, so I'll start from the begining.
    I started hearing a rattling noise from the engine compartment every time I turned on the A/C, which subsided after driving. Around that time, it was blowing hot air in the rear compartment. Then I began to hear the rattling even with heat/defroster. Finally, I'm getting hot air from the front. I checked the fuses and all appear good.
    Any advice/help would be appreciated.
  • jpw5jpw5 Member Posts: 1
    I have a 2007 Yukon Denali that is blowing warm air on the driver's side when temperature is at 60 degrees, (as low as it goes). It will occasionally "kick in" and blow cold air. It blows the normal cold air on the passenger's side all the time. I've taken it to dealer three times now and they can't figure out the problem. The first time to the dealer, they added freon. The second time, they replaced the actuator. The third time, they said they couldn't duplicate the problem and don't know what to tell me. It's still blowing warm to very warm air. This is very frustrating since I live in Texas. It's hot! Don't have time to run to dealership when hot air kicks in. I think they should have a way to troubleshoot this problem without having to "duplicate it" as they tell me. Any suggestions?
    Thanks. Also, don't know if this matters. The battery went totally dead and was replaced approximately eight months after I took delivery of the car.
  • boglesbeeboglesbee Member Posts: 1
    2007 Yukon. Bought at Texan GMC in Humble. I have had several problems with my AC system. Like the problem you describe, I have experienced problems with the AC kicking in/out. No rhyme or reason. Please let me know if you have found a solution to your problem....dealership has proven less than helpful. Seems unreasonable to have these problems in a $40,000 vehicle.
  • kjchmaykjchmay Member Posts: 1
    I am also experiencing this same problem on my 07, with the dealerships lack of knowledge and attempt to just throw parts at it with no success. My theory is a mixing door is stuck for some reason as it will get hot when you run the temp up, but will not get cold when you run the temp down. It only is on the drivers side. I am going back to the dealership tomorrow for the third time. The next visit I may be tempted to drive it through their wall and give it back to them.
  • delay275delay275 Member Posts: 1
    Within the past 3 weeks have noticed a new glitch. When running the a/c it will sometimes blow hot air out of the front as well as rear a/c vents (it has dual a/c). I reading of other peoples issues, it seems like on their vehicles it's just the drivers side that does this. On mine, its left, right and rear. I've replaced the fuse and relay in the underhood fuse box, but the same symptoms exist. I've cycled thru the temp range thinking it's maybe a piece of crud in the mixing box jamming one of the doors, but that doesn't do anything. But if I turn the vehicle off for alittle while and start it back up and turn the a/c backon it works just fine. HOWEVER, (this is the weird part) the air is 5 degrees cooler than it's ever run before. On the day I baught it it put out 55 degree air and it's been that way ever since. I just chalked it up to "just the way it is". But now, when running properly, it puts our 48 degree air. I took it to our local auto air conditioner center and they couldn't find out anything wrong. They were unable to duplicate the issue and said that 48 degrees was supposed to be the norm, and they said that it was probably a bad mixing box and when I got good and tired of it flaking out for me to come on back and they'd replace it. He said that it was a [non-permissible content removed] of an item to repair. After I left, I got to thinking, if hot air came out of the front because of a bad mixing box door issue, why was hot air coming our of the rear vents too. It has it's own mixing box. Just today if was flaking out again and I decided to see what the internet has to say about this anomoly. Other than this single issue and a replaced water pump I've had zero problems with my Yukon XL. I must be one of the lucky ones that picked one that wasn't a lemon.

    If any of you have any insight as to what migh be my problem I'm all ears (eyes).

  • lpfeiferlpfeifer Member Posts: 8
    You never said if the compressor is running when the hot air is blowing?? Also, there is a switch for low freon on the silver canister for the air conditioning on the right side under the hood. You can pull off the wire connector and jump it with another wire to see if it is sensing low freon and not allowing the system to work. How many miles?
  • lpfeiferlpfeifer Member Posts: 8
    Sounds like your compressor is gone, or at least the clutch that kicks it in and out.
  • jlflemmonsjlflemmons Member Posts: 2,242
    Under the hood, pull the A/C fuse and wait about 10 minutes. Put it back in and start the car, put the A/C in the 'auto' mode. It will act a bit weird for a few minutes, then it should straighten out. This is the exact same scenario I went through when replacing the battery on my '04. Pulling the fuse forces the ventilation computer into a hard reset and self learn mode. Haven't had a problem one since doing this a month ago.
  • fivebyfivefivebyfive Member Posts: 1
    My heat has not worked for several months now, but with cold weather coming I need to get it fixed. A/C works fine for cooling when weather is hot.

    I recently had a new water pump and t-stat installed as part of a non-related repair, but no-heat problem was not solved. Operating temps seem to be within normal parameters. Water supply line to heater core is very hot, return line is ice cold. Possible plugged inlet to heater core? Seems possible, but not probable. Somebody suggested that I look at the actuator(???). Any other suggestions?
  • dreabtdreabt Member Posts: 1
    Hi my name is Andrea,
    My Yukon is doing the same thing. I was wondering did you ever get your fixed and if so what was the problem. Please inform me because I have not had my Yukon for 4 months and the dealer is about to get it all.
  • rayb6rayb6 Member Posts: 1
    Picked up vehicle last Sunday with 300 miles on it. When I restart my 2007 Yukon xl (Not Denali), my heat only comes on after I change the heat settings a few times. The temp gauge is up to near 210 but no heat. I have to adjust the flow direction. Went to the dealer yesterday and they said it was normal. Any suggestions would be helpful.
  • fireballsfireballs Member Posts: 2

    Thanks for the great tip! I recently replace my battery on my '04. Well, when heater is turn on the passenger side blows Hot air but, the driver side blows Cold air; "very cold".

    I called the dealer and they didn't have a clue but wanted to keep my GMC for a few days.

    I think your reprogramming will reset the system. . .thanks --Los Angeles, CA
  • eodmaneodman Member Posts: 7
    Mine is a little different than everyone elses. when it's cold out.. say in the 20-30s it takes forever for the defrost to start blowing... either hot or cold...

    in the summer sometimes it takes mins. before the a/c will blow....

    no problems with air temp.. just the time lag for it to blow any air at all...

    anyone have a clue?
  • lpfeiferlpfeifer Member Posts: 8
    This sounds kind of like my problem with the 01. Due you have the auto climate control? Does the rear blower work, even if the front one does not? Let me know this, and if this is the case, I might be able to help you.
    Lyle Pfeifer
  • eodmaneodman Member Posts: 7
    yes.... rear works as designed and the front is the only one that gives me problems. it has auto and i'm tried the fuse reset... maybe i'll try it again just longer.

    ok this morning it was cool 45degrees and it took awhile to come on. now it's 65 and it will turn on real quick... if it's 100 the a/c will take awhile to blow

    but rear air is normal in all aspects
  • eodmaneodman Member Posts: 7
    :cry: come on now?????? nobody has any ideas?????
  • tidestertidester Member Posts: 10,059
    Maybe the fan is "gummed up?"

    tidester, host
    SUVs and Smart Shopper
  • eodmaneodman Member Posts: 7
    not sure... it works and works well.. but, it has to finally decide to turn on and once it has been going for awhile it will turn on instantly.
  • lpfeiferlpfeifer Member Posts: 8
    Do you have dual air/heat?
  • lpfeiferlpfeifer Member Posts: 8
    There is a plug that goes into the AC/heater fan. You have to remove a cover that is held on with 3 or 4 screws and you can see the fan motor. This cover goes from the passenger side all the way to the middle of the tunnel. The plug is on the right or inside of the fan and kind of hard to get to and remove. The fan is located on the passenger side of the car, the plug, if like mine is shorting out. It is connected to a box or block, similar to the resistor block on a non auto climate control unit. Yours runs about $130.00. I replaced mine as the plug melted due to being installed wrong. Look inside the plug for bunt contacts. One of mine, the main power point was pushed all the way down and did not spring back up to allow good contact, causing a high resistance and heat build up causing the plug to melt. If you pound on the cover about 1 foot over from the passenger side wall with your hand, your fan should start. But remember, this plug is getting hot. This is at least what happened to mine. Worse case, if you need a new plug, you have to buy the harness just to get the plug, I think they said about $165.00.
    Hope this helps. Let me know, as I had this problem with a 2001.
    Lyle Pfeifer
  • eodmaneodman Member Posts: 7
    thanks for the info... i'll check it out and let you know if it worked
  • eodmaneodman Member Posts: 7
    i have dual zone in front and rear air/heat in the back. I will take a look at the plug this weekend if i get a chance.
  • fireballsfireballs Member Posts: 2
    Well guys,

    I remove the fuse and waited few minutes before replace it.

    It didn't work. I still have cold air blowing on the drivers side and hot air blow from the passenger side/. Any Ideas
  • moterymotery Member Posts: 5
    Hey guys!!
    I have a GMC Yukon XL ’02 and it was fine with me until today, I drove to work (it’s about 20 minute drive) and after I park it I turned it off, then suddenly the AC turned on as if it on Auto, I tried ever thing to shut it down I remove the large gray fuse and small 10amp fuse under the hood and the AC still works I turned the SUV on and I couldn’t even control the AC it seemed it has a mind of it's own.
    finally I unplugged the battery and guess what … it works the damn thing went back to normal. my question is what the hell is wrong with my SUV… !!????
  • tidestertidester Member Posts: 10,059
    Are you sure it was the air conditioning that was running or was it just the air conditioning fan? The fan will run off the battery/alternator which suggests that your fan switch is faulty. The compressor does not run off the battery.

    tidester, host
    SUVs and Smart Shopper
  • moterymotery Member Posts: 5
    no it was the fan only ... well thanks a lot pal... it seemed that the fan switch is damaged... :)
  • bbebenseebbebensee Member Posts: 3
    All of the rear air vents push out cold air where as the front control works just as it is suppose to. Is it a matter of resetting the computer or is it mechanical. The dealer wants $900.00 to possibly fix the problem?
  • denali00denali00 Member Posts: 1
    I have a 00 denali yukon and the heater does not work properly all the time. Please let me know if you have experienced any of these problems with your vehicle
  • obyoneobyone Member Posts: 7,841
    You could disconnect your battery for 15 minutes to see if it resets. After I had replaced the rear evaporator core, the system needed to be reset for the rear controls to work correctly.
  • obyoneobyone Member Posts: 7,841
    Try and check your coolant level. If the level is low the heater will not operate correctly.
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