hi,i have 2006 hhr.when i turn controls to vent i still get warm air and then i will be driving and all of a sudden the vent air starts to work for a while and then back to warm air.same with air conditioning.i will turn on air,get air for a while and then no air and then air again.some times i hear like a vacuum opening up.oh for the old days of cable vents...open or closed ,no problems!anybody know what causes this and how to fix?love my hhr!thank you

 

OK. If I'm understanding this. Turning on the vent air or AC, the air from the vents is going from cold to warm on it's own. You said "no air", but I'm assuming it is still blowing from the vents.
Sounds like a possible blend door problem. If you are not knowledgable in automotive AC's, this one is best left to a professional.
Even to diagnois this will require going behind the dash. All of the controls and ducting are nicely hidden behind the dash area.
A 2006 with ? miles. At this age it could use a AC system checkup also.

 

X 2

It sure does sound like a blend door problem, or a possible failure of the switch/knob assembly.

 

I believe those damper/blend doors are vacuum operated. If there is a vacuum leak, or the one way valve has failed, it would tend to change the door positions when accelerating. Do you notice that change most noticably when accelerating, or is it completely random?

 

Thank you for taking the time to share your knowledge. I was thinking about the air conditioning check up too, but since I am not a technician I am not able to offer ideas such as that.

I hope you had a great weekend.