Shouldn’t both charge voltages be higher? 12.8 while the car is on seems low, no? So does 12.4 when resting. I thought 12.8 resting was more appropriate and mid 13s while charging?

 

GBCM (Generator Battery Control Module), controls alternator voltage and yours is working like it should.

More info here:

https://www.hummerforums.com/forum/h...m-43179/page2/

https://srs20assets.service-solution.../TL_Sept04.pdf

 

So I had an extra HVAC controller lying around - who doesn't haha. I bought it last year when I was messing with the "one click from cold" problem along with an issue with my blend door actuator. This problem ended up being a severed reference voltage line so I did not need the HVAC controller then. I decided to pop that in today to test but it would not calibrate. I had some 68 ohm resistors around from the last round of issues so I put one in-line with the blue/black wire and then the system would calibrate. AC functions properly now on all blower speeds. I will report back if that changes. Thank you again for the assistance.

 

I don't have an extra HVAC controller laying around and I never installed a resistor? Mine is still OEM and works perfect to this day.

 

Curious, what's the production date on your '07? Mine turned 14yrs old, last month (08/06)

 

[QUOTE=hummerz;377811]Curious, what's the production date on your '07? Mine turned 14yrs old, last month (08/06)[/QUOTE


The AC was working all day today until just now. I am so frustrated. Any other recommendations?

how do I find the production date? It’s not on the sticker anywhere that I can find..

 

Did you change the battery terminals?
Production date is on the rear of the drivers door jamb.

 

I finally got around to changing the battery connectors. AC is working consistently now. Yah. Thanks for the help.

our hummer was made in the same month as yours.