Hello all,

I have a 2009 GMC Sierra 1500 6.0L with 122,xxx miles, equipped with the automatic climate control system. Starting in fall of last year I began to have issues with the climate control, where it would become "stuck" on a given setting and temperature. The dash unit will read a given setting, but the system refuses to change modes and/or temperatures. The system will work fine intermittently.

For instance, it will get stuck on feet/cold, or dash vents/hot, or any combination thereof (right now it is stuck on floor/dash and ambient temperature air). The fan speed works just fine. In fact, if it is on "auto" and the system is stuck, the fan will blow a given speed as if it were trying to work correctly.

I have replaced:
Drivers side blend door actuator
Drivers side temperature actuator
Passenger side temperature actuator
Cabin air temperature sensor
In-dash control unit

I have done the reset/relearn procedure more times than I can count, both through pulling the fuse and pulling the neg battery cable. It helps (sometimes) but only works for a few minutes.

I am at my wit's end. I've searched and searched, but no one seems to have this same problem. Lots of failed actuators, but replacing the actuators fixes the issue.


I don't have a way to read BCM codes, is there a cheap reader or software out there that will pull them?

Also, does anyone have a wiring schematic for the HVAC system that they can share?

It's almost like it's a short somewhere in the harness. I guess my next step is to take the dash apart and see if I can find a short. This thing has been a complete sh*tbox, from a cracked dash to ticking lifters to dead door lock actuators and now broken HVAC. Part of me thinks it is time to give up and go buy a Ford!!

 

On auto it will blow just on your feet until the cab is the right temp. Then it will do vents and feet.

And when its hot it doesn't the opposite and blow vents first then once it reaches the right temp it will blow both vents and feet.

It can take a long time before it starts blowing both.

When I first got my old LMM I thought it was broke until somebody explained that to me.

 

Even if I don't have the system on auto it won't change modes or temperatures. This past winter I dealt with ice cold air blowing out of the dash vents for a few weeks, then got face melting hot air for a few more.

Selecting different temperatures doesn't change the temperature of the air coming out of the vents. Selecting different vents doesn't change which vent the air comes out of (defroster included).


Prior to this issue (and when the system happens to be working randomly) I could select whatever temperature setting and vent setting I want and I get it. Trust me, it's not working correctly.

 

Got just making sure

 

The lowest priced scan tool I have seen is the Autoenginuity. You can get GM specific advanced coverage.

You have to buy basic scan tool for $249.95 then its another $229.95 for the advanced GM coverage.