Hi!

I believe it's quite common issue, but the heating is working only when it's set to maximum. Is it 100% of the HVAC Control Module issue?
I'm still troubleshooting, and I can only see the differences in voltages on the light green wire. I still haven't figured out where it goes. If the heat is max, then I get 3V on it, when the temp is on something else, I get max 0.7V.
I can also see some heat spread on the PCB board under the 100 Ohm resistors, but they work just fine.
Can anyone tell me, what are they usually repairing on these boards? I could do it myself, but I just can't find the fault anywhere.

Thank you!

 

Rajareits just trying to understand what your issue is.

Are you talkng about the blower motor (fan) speed?

Which PCB are you referring to?

The attached circuit diagram may help.

 

Thank you! I can now test the board, or bypass it that is.

I'm talking about heat, the temperature. Fan works fine. I only get warm air on max temperature setting.
PCB was the HVAC module.
But of course, I couldn't wait, so I ordered a used replacement already. Let's see how it goes.

Thank you!

 

Never actually been there BUT if its a light green wire, it looks like the right air actuator. If so this wire is the position feedback of the motor position, so it could be a problem with the actuator itself. These seem to be a common issue.

Other members may be able to advise you more accurately.

 

Yeah. I changed the HVAC control module, this didn't fix the issue.
I will check the actuators tomorrow. First I need to understand of course what the actuators do..
Thank you!

 

Perhaps this PDF will help

 

I already found this from you on another thread. What else are you not sharing with us?
This for sure helps.

Funny thing is.. The car says "ice possible". So I checked my ambient temp sensor. I think they work okay. Both of them lowered their resistance the same way as the other one, and both had the same values. I see correct temperature with both sensors on the rear view mirror aswell.
But where does the instrument cluster get it's info on the outside temperature? And for me, it doesn't make sense. The instrument cluster thinks it's freezing outside, and at the same time, the HVAC thinks it's super hot inside, so it starts cooling straight away when I turn it down from the max. What gives?

Tricky to get the diagrams also. Would you happen to have a bigger manual you would like to share?

Thank you so much!

 

Wire ref 735 I believe is the outside "ambient" temperature.

The mirror display I believe is separate and not related to the HVAC system.

This is all the info required I believe, a Tech 2 diagnostic scanner might prove very useful.

Don't believe there is a single full pdf that covers everything, for example the HVAC operation and wiring diagram came from seperate sources, I'm not holding anything back that I'm aware of.

 

I hope I just may have some wiring issues. I will check now and let you know.
No Tech2 here unfortunately.

I don't understand yet, where does it take the info for "ICE POSSIBLE" message?

 

Trying to follow the wires no. Super difficult to find where something goes.

The "ICE POSSIBLE" message is coming from the new spare HVAC Control Module which I got from an Escalade. With the original one, I don't get the message.