We are loving the hummer but as summer wanes we need to tackle this next issue. I found several old threads but none seemed to have the definitive fix.

When on full cold AC it works great. One click off full cold and it gets hot! Real hot instantly. How do we fix this?

 

I have seen this exact thing happen twice - my understanding is it means your HVAC control board is dying (or at least having trouble managing the proper resistance) so it puts it into an 'emergency mode' hence the almost all heat for all but one click. Follow these steps exactly. Easy as pie. You won't believe it.

https://www.hummer4x4offroad.com/for...te-Control-fix

 

Did your H3 have the HVAC recall work performed?

 

I don't know, maybe I should check on that

 

@Doc Olds knows the H3 a lot better than I but I can say the cases I worked on the recall was completed (years before the temp issue) and this resistor in the HVAC board indeed did the trick

Having said that - the recall is a serious issue and should be addressed as well. It will get hot, burn/melt and may cause you to lose blower power (if not much worse). In either case, both items are easy to reach and easy to work on.