Any chance you are using defrost or recirc when you are experiencing cold air?

 

To be honest, it happens regardless if defrost and recirc are off or
on. I tried it each way to eliminate if it would only act up one way but it's the same. When I have the blower on, like say setting 2 and it's blowing lukewarm air, it blows more as if more air is coming through then when it's blowing hot. When it turns too hot, I feel the level of air kick down a bit. Just an observation......

 

I just read through the blend door thread. It seems there is a calibration involved. It may need to self calibrate every time the battery is disconnected. You could try disconnecting and let it try to self calibrate again. It may turn out that you have a bad HVAC head unit, but we're not there yet.

 

The reason I asked was because either of those things turns the A/C on without any indicator light.

 

Ok, I'll give that a shot. Yea, I don't want to throw more stuff then I have to at it until we have ideas.

 

SOUNDS LIKE A BLEND DOOR MALFUNCTION AT RANDOM MOMENTS. Had same problem with ours and guess who fixed it....."Chevymgr" at Reliable Chevrolet in Richardson Texas.

 

Is the blend door reasonably priced? I'll throw one in it......

 

well the part number from our common parts thread is 52411441, which doesn't turn up much on google, one used part on eBay 52411441 08 2008 CHEVROLET HHR HEATER BLEND DOOR ACTUATOR MOTOR #C-48 | eBay

The number turns up no results on wholesalegmpartsonline.

It's a little difficult to tell, but looking at the exploded diagram, and the orientation of the heater core lines, it looks like this is the part number 10393075.

ACTUATOR. AIR CONDITIONING (A/C) Control. A/C & HEATER MODULE ASM; HEATER for Chevrolet HHR (2005 - 2011). #10393075

Looks like there is a Dorman part number, 604-133

 

Ok! So I just drove to the store, ran the heater and is working as should lol. Definitely intermittent. Cycled all the settings, cycled fresh to recirc, all blows hot.

 

Well, keep us posted, hopefully it was just one last air pocket that worked itself out!