Another HVAC issue post...

[AllenBrowning]

Hello all, I’m having an HVAC prob in my 2002 Yukon xl slt. HVAC is stuck on defrost/heat/outside air. No controls work. All rear ac/heat/fan/mode controls work perfectly. This is only the front cabin area. I’ve searched and searched this forum and all through YouTube and other internet sites with no success pertaining to this actual prob. I found the mode door actuator broken and have replaced it. Did the recalibration sequence more than 10 times with no success. Checked the blend door actuator and it is good. Pulled the dash apart, removed the air duct to get access to the recirculating actuator, removed it and checked it’s function. It works properly. It’s my understanding there are 4 actuators. The other one is supposed to be behind the radio/climate control cluster but I do not see one. What am I missing. Temps are beginning to heat up and I need to get this fixed for my family. Any help is greatly appreciated!

 

[OR VietVet]

First: Welcome to the forum from Oregon.

Second: Hopefully it isn't anything like this: https://www.rockauto.com/en/moreinfo.php?pk=85886&cc=1381069&jsn=3496

Third: We recommend that you put all your rig(s) info in your signature so we all don’t have to guess at year, make, model, engine size, trans, rear axle locker…….etc. Makes it way easier on all members that attempt to help, to have that info right up front. It is also recommended that you take a pic of your RPO codes, on the inside cover of the glove box, and post that image in your signature. All this info will greatly help those that will try to help with a problem.


If there is any other info, like upgrades, mods or recent mechanical/maintenance work done, that would be helpful in any post as well. Too many times a question is asked by the poster and after about 10 responses we find out that the poster has done recent work to attempt to fix the problem or work that was done that SEEMS not related to the problem.

 

[Fless]

Welcome to the forum, Allen.

Could you describe the recal sequence you used?

If you have access to a Tech 2 or other bidirectional scan tool, you could use the tool's HVAC reset procedure. What part of the country are you in? Perhaps a member with a Tech 2 could arrange a meetup.

 

[AllenBrowning]

Oh sorry I didn’t realize. I’ll update everything as soon as I get the info. 2002 Yukon XL SLT 2WD 5.3 auto with tow package 36,000 miles. Everything is all factory. But yes it’s elect climate control. The image in the pic is the same as what we have. My next step was looking into replacing the control module but was hoping it was just an actuator as that’s what all the other posts I’ve read lead to. I suppose I’ll start putting everything back together and look at ordering a module.

First: Welcome to the forum from Oregon.

Second: Hopefully it isn't anything like this: https://www.rockauto.com/en/moreinfo.php?pk=85886&cc=1381069&jsn=3496

Third: We recommend that you put all your rig(s) info in your signature so we all don’t have to guess at year, make, model, engine size, trans, rear axle locker…….etc. Makes it way easier on all members that attempt to help, to have that info right up front. It is also recommended that you take a pic of your RPO codes, on the inside cover of the glove box, and post that image in your signature. All this info will greatly help those that will try to help with a problem.


If there is any other info, like upgrades, mods or recent mechanical/maintenance work done, that would be helpful in any post as well. Too many times a question is asked by the poster and after about 10 responses we find out that the poster has done recent work to attempt to fix the problem or work that was done that SEEMS not related to the problem.

 

[AllenBrowning]

Oh sorry I didn’t realize. I’ll update everything as soon as I get the info. But yes it’s elect climate control. The image in the pic is the same as what we have.

Welcome to the forum, Allen.

Could you describe the recal sequence you used?

If you have access to a Tech 2 or other bidirectional scan tool, you could use the tool's HVAC reset procedure. What part of the country are you in? Perhaps a member with a Tech 2 could arrange a meetup.

thx for the response. I don’t have access to Tech2. I have read about that and would be a great help for this I’m sure.

The recal sequences I have done are the battery terminal unplug, discharge residual power, turn fan off, set to cold and front vents, reconnect terminal, switch to ON, allow actuators to cycle. Another way was pull the HVAC1 fuse and discharge power then reinstall and perform the same control setup. Doing these steps would cause the actuators to cycle however I let this run for more than 15 mins at times and they never completed the cycle. I removed all actuators, checked continuity, ran a +\- lead from a 9v battery to the appropriate pin terminals of the actuator to check for functionality. All checked out normal. This is what brought me to searching for a possible hidden actuator. I’m told there’s 4 however I only found 3. Mode, blend and recirc... I’m stumped.

My next move was ordering a replacement climate control module. I know the ac works because it blows to the rear. Right now I have all the actuators manually set to front vents/ac/outside air. I’ve kept them unplugged so they don’t revert back to default.

 

[AllenBrowning]

Here is the parts code from the glove box

 

[OR VietVet]

Here is the parts code from the glove box

View attachment 243864

Put that in your so it shows every time you post here. Not needed right now but may in the future.

 

[TJ Baker]

ran a +\- lead from a 9v battery to the appropriate pin terminals of the actuator to check for functionality. All checked out normal

So I'll go right ahead and say that what I have to add might not apply as my experience is more on another GM product, the GMT360 (Trailblazer). However,,, when the trailblazer recalibrates it runs the actuators in each direction until they hit a hard stop. Just running it a little with a battery will not tell you if the internal gears are busted or cracked in such a way that will prevent a hard stop from occuring. In the case of my trailblazer the actuator motor would keep turning while internal parts slipped and would never successfully calibrate.

 

[swathdiver]

Hello all, I’m having an HVAC prob in my 2002 Yukon xl slt. HVAC is stuck on defrost/heat/outside air. No controls work. All rear ac/heat/fan/mode controls work perfectly. This is only the front cabin area. I’ve searched and searched this forum and all through YouTube and other internet sites with no success pertaining to this actual prob. I found the mode door actuator broken and have replaced it. Did the recalibration sequence more than 10 times with no success. Checked the blend door actuator and it is good. Pulled the dash apart, removed the air duct to get access to the recirculating actuator, removed it and checked it’s function. It works properly. It’s my understanding there are 4 actuators. The other one is supposed to be behind the radio/climate control cluster but I do not see one. What am I missing. Temps are beginning to heat up and I need to get this fixed for my family. Any help is greatly appreciated!

The Tech-2 eliminates any guess work into what is going wrong. There are two temperature actuators, one for the driver and passenger. The driver's side actuator is under the passenger footwell, just to the right of the center console and left of the cabin filters. The passenger side is directly above, more or less, accessed through the glove box usually. The guts are the same but we have different generations so consider that. You correctly identified the other two, Mode and Recirculate.

Even after researching these actuators for three years, I still came across conflicting information. Several GM dealership websites and ACDelco all gave conflicting information. The first actuator purchased was the wrong one of course. Ordered the other and all was well. When the wrong one was in, AC was blowing hot, counts were backwards almost like we put it in backwards which is physically impossible.

On the GMT900s, if you replace the main control unit, it has to be programmed. Not plug and play.

 

[AllenBrowning]

So I'll go right ahead and say that what I have to add might not apply as my experience is more on another GM product, the GMT360 (Trailblazer). However,,, when the trailblazer recalibrates it runs the actuators in each direction until they hit a hard stop. Just running it a little with a battery will not tell you if the internal gears are busted or cracked in such a way that will prevent a hard stop from occuring. In the case of my trailblazer the actuator motor would keep turning while internal parts slipped and would never successfully calibrate.

View attachment 243878 View attachment 243879 View attachment 243881

thx for your response. Your pics show what I first experienced for the mode door actuator. Broken gear. I replaced that one several months ago which did not remedy the issue. Which is what took me attempting to locate all other actuators. I removed the blend door and recirc actuators. Opened the cases and checked for broken gears. All checked out fine. I did a function check with a 9v battery and all work properly. Never could locate the 4th actuator. All research shows it on top of the hvac system but I never saw any indication of that. So I’m stuck. I’ve replaced all actuators even tho the others checked out fine