Climate Control Questions

[Marshall2002]

Hello all. I have 2 issues with the climate control system on my 2002 Yukon Denali (438k) that have turned into big mysteries for me and my mechanic.

1. The mode actuator for the front control will not move off of vent. I cannot move it to floor or defrost. When I turn the control knob, I can see the actuator move about 1/8” and stop. We have replaced the actuator twice, and the control head without any change. Everything else works fine (fan speed and temperature). Any ideas?

2. On the rear climate control, the blower will only run on high. Low and medium have nothing. I have also replaced this control head with no success. Temperature and direction both work fine. Any ideas?

 

[Marky Dissod]

Any ideas?

Inside your glovebox are a bunch of thre-character RPO codes.
It'll be easier to answer your questions if you provide the RPO codes that start with 'C'.
Example: C36, C60, C69

 

[Joseph Garcia]

Post a photo of your RPO code sticker inside your glove box.

 

[Fless]

I've not dealt with an issue like this, but if the mode door actuator appears to be commanded correctly, but doesn't move much, perhaps the mode door is stuck or blocked somehow. Might be worth removing the actuator and trying to move the mode door manually.

Using a good bi-directional scanner on it to command the actuator might give a clue as to what's going on.

 

[Doubeleive]

i'm with Fless, try moving it by hand, if it is stuck, well then that sucks because that means the dash has to be removed to fix it as far as i know.
as for the rear there is a rear command box module, which may be the issue. It is behind the passenger side rear hvac cover and forward of the rear actuators. (follow the wire harness)

 

[Fless]

The "rear blower on high only" issue is likely the blower resistor module; the output of the resistor -- through the various speeds -- can be measured with a voltmeter at the blower motor connector.

 

[Marshall2002]

As for the mode actuator, I can freely move the doors from floor to defrost by hand, so the doors are not stuck.

As for the rear blower switch, would not the resistor be changed when I changed the entire unit out with the same results?

 

[Marshall2002]

i'm with Fless, try moving it by hand, if it is stuck, well then that sucks because that means the dash has to be removed to fix it as far as i know.
as for the rear there is a rear command box module, which may be the issue. It is behind the passenger side rear hvac cover and forward of the rear actuators. (follow the wire harness)

The mode doors move freely by hand. So it’s not stuck. I’ll check the command box for the rear control. Thanks for the feedback!

 

[Marshall2002]

I've not dealt with an issue like this, but if the mode door actuator appears to be commanded correctly, but doesn't move much, perhaps the mode door is stuck or blocked somehow. Might be worth removing the actuator and trying to move the mode door manually.

Using a good bi-directional scanner on it to command the actuator might give a clue as to what's going on.

It moves freely by hand from floor to defrost. The scan doesn’t not reveal any issues.

 

[Doubeleive]

It moves freely by hand from floor to defrost. The scan doesn’t not reveal any issues.

does the actuator move all the way when commanded? if not then it is no good, oem or dorman are recommended.
also your scanner should show a bXXX code with a count of how many errors it has detected

 

[Marshall2002]

does the actuator move all the way when commanded? if not then it is no good, oem or dorman are recommended.
also your scanner should show a bXXX code with a count of how many errors it has detected

When commanded, the actuator moves about 1/8” and stops. My mechanic installed 2 new Dorman actuators with the same results. I installed 2 controller heads with the same results.

 

[Doubeleive]

When commanded, the actuator moves about 1/8” and stops. My mechanic installed 2 new Dorman actuators with the same results. I installed 2 controller heads with the same results.

i would make 100% sure the correct actuator is being used, some look exactly the same but are internally different, that alone could be the problem.
I would also command it while not physically installed. (harness plugged in only)
the whole purpose of using the scanner is to see actual vs commanded, It can say it is working just fine but until you see it with your own eye's, then no telling.
if the wrong actuator is used it may only move part way or may be reversed.

 

[nonickatall]

Sound to me like a calibration problem.
Did you calibrate the climate system? There is procedure for that...

The back blower is for sure the resistor like Fless already said..