Hello and thanks for any advice on this. I have a 2008 Hummer H3. Having a weird heater problem and hoping you can point me in the right direction. I am getting no heat at all. AC works great. The first thing I did was check coolant - it's full. I then did a heater core flush to make sure it wasn't clogged. I know it's not the thermostat, temperature reads fine, heater hoses getting hot.

The weird part is the selector switch for where the air blows (face, feet, defrost, mix of both) won't do anything except come out thru the vents on the dash. When I move it to floor or defrost it just stays blowing out the dash.. The selector for strength of the blower - low to high - is working but not the selector for where it blows. No heat at all, just cold air. I'm thinking it has to be electrical but would like you all to weigh in. Thanks for the help.

 

First make sure temp at the heater core hoses inlet and outlet match coolant temp! Check feel/listen to the air mode control actuator #32 when you switch air flow positions. Same with blend door actuators when you switch temp control #30x2. The air inlet actuator (#4) should close when pressing the (air-recirculation) center button, blocking outside air from entering the cabin.

 

Thank you Hummerz, Temp is the same (heater hoses and Coolant). It must be the Actuators, can't hear anything when moving dials.

 

Check/clean/reseat connectors/contacts, also tap test the actuators while switching controls. Btw, how much heat does one need in AZ?

 

I will give it a try. Thanks again. Good point on requiring heat in AZ. Its been a little chilly in the mornings here - high 30s low 40s. Then I like to head to the mountains in Flagstaff. It got a little uncomfortable when I woke up in the morning and it was 8 degrees outside. 🙂

 

FYI, TAP TEST

 

I had a weird thing last week with the Snow that hit Virginia, Went to take the Wife to work and nothing but Cold air blowing, Thinking Dam, something else to fix, this was really the first time I used the heater since I got the truck in August.
9 hours later, went to pick her up and Heat is blowing just fine, Been working ever since. I guess the cold has an impact on these old trucks, Drove it 200 miles the other day and kept getting the SERV TPM light, sat overnight, it was gone, Drove back home and it came on again, sat overnight again and it's been off ever since. I had actually reset the TPMS back in October I think it was, after putting New Tires/Sensors, worked fine up until the light came on.

 

Poor and deteriorating electrical connections are caused by the age of these trucks. When was the last time you put air in the tires???

Air the tires all to exactly 38PSI cold.