Hi everyone,

I recently picked up a 2003 Hummer H2 and it seems to have the dreaded cold on one side and hot on the other issue...

I've been trying to diagnose this for weeks now and I can't seem to pin point where the problem is. When I first picked it up, I had torn the dash apart to replace the passenger side temperature actuator (the fun one on top of the A/C box). When I got everything back together, the issue persisted. I then tried replacing the HVAC Climate Control Module with a cheap one off of Amazon. It initially fixed the problem, and I was getting heat and A/C on both sides. But fast-forward a few weeks and it crapped out on me again. So I bought a refurbished OEM one off of EBay. I threw it in and immediately noticed that it was broken still (the potentiometers were erratic and the system seemed to be stuck on defrost mode and it wouldn't blow through any of the vents on the dashboard). So I returned that one and bought a different one that showed up last week. Got it installed, and everything seemed to work control-wise on the module, but I'm still having the original issue. I hooked my scan tool up and confirmed that none of the actuators seem to move when I command them with the ***** on the module. Additionally, my left temperature motor seems to constantly fluctuate between 23 and 234 on the "Left Motor Mix Commanded" PID. I tested continuity from the 24-pin connector to both of the 5-pin actuator connectors and they all seem to check out. I've tried re-calibrating the actuators and they do initially both go hot, but then move to cold and get stuck there and won't respond to being commanded on or off on the scan tool or ***** on the module.

Does anyone have any insight on what could be the issue here? Logically to me, it seems like it can't be the actuators because they seem to turn when I re-calibrate them. But maybe I'm looking at this entirely wrong at this point. Any insight would be extremely helpful and appreciated.

Thanks,
Zach

 

if you went through that many modules and still have the issue i would suspect the actuator.

 

BRONTECH - up kinda early!!! LOL

ZACH - I experienced pretty much the same last year. AC wasn't getting real cold. After shop replaced every component (compressor, condenser, dryer, etc) it still wouldn't get freezing and still wouldn't operate the fresh air actuators. So I replaced the actuator. No change. Replaced the HVAC CONTROL UNIT with an Amazon unit. Actuator worked but AC went from fairly cold to warmish. Returned for another Dorman unit and it wouldn't operate the new fresh air actuator. By this time I had learned how to test/reset actuators and knew it wasn't that. Put original unit back in and shop tried to "set things" with Tech 2 but no joy. The shop finally put in a fourth unit purchased from their local supplier (also a Dorman) and it self-set everything perfectly and is still working great. BTW - turns out the 2 OEM actuators replaced were good - had just been driven to stops. There is a Y-tube video shows how to test and get them reset to center for installation. They are supposed to be in "center position when installed, so if one is at an end or stuck then the Dorman units won't be able to get them all into appropriate "sync" position during the initialization process.

 

Gotcha, yeah sounds like we’ve both had a similar route then. Just for kicks I replaced both temperature actuators with new Duralast ones from Autozone and no change. So at this point it HAS to be the HVAC module I would think. I’ll give the Dorman one a go and see if I have any luck. Thanks for your help.

 

Adding a note for the 08/09 H2 drivers in case any of you are having a climate control HVAC problem. You will find that there are no official Dorman remanufactured units. In fact I called them and asked, and they said the 08/09 H2 was not supported.

• For 2003-2007, Dorman have the 599-015 and the newer 599-211XD units available (Look for HVAC Control Module)
• For the 2008-2009 - they only have the actuators. No HVAC Control Module

Part number 599-138 supports the 07-09 Tahoe and 07-09 Yukon, and I took a chance on GM not spending extra to create a completely unique HVAC system for the 08/09 H2... and I can confirm that the 599-138 works in a 2008 H2. It appears that all the functions and buttons work properly. I confirmed that it worked in tandem with the rear HVAC control in the console/ Limited testing at this point, and no guarantee that it won't cause some issue down the road...

 

The climate control module I also have is also hit or miss (2x purchased Dormans). I have one now that works 99% of the time - although I am sure its responsible for giving me a "ICE POSSIBLE" warning at start up occasionally on dash... while its 90 degrees outside - lol. Yes- I have replaced the sensors at bumper (twice).. started occurring after the second dorman climate control change.