I am not on here a great deal in posting, but I am on here to read/learn. I have been reading posts I thought might be related, but could not find a match to my problem. Soooo, I have a 2010 HHR SS. For the last month the heater/A/C blower has gradually diminished to putting out very little air through the dash vents. It is now nearly only 10% of each of the original blower settings, from low to high. I began investigating by turning the A/C off and blowing just air. Same diminished output through the dash vents. Then with heat. Same results. Then I selected the air flow output to the floor, defrost, and combo of floor and defrost. Heyyyy, I have a high volume of air from those three as original. I thought, then why not the dash vents? Blocked? Vent pipe have holes? Etc. Then, when I went back to the A/C dash selection to reexamine the original problem it disappeared and the HHR SS blew full as it was designed. My question is, what does this tell me? Is the directional control switch bad, needs cleaned with contact cleaner, or something else? Any direction from all the "senseis" would be helpful. Thank you for all the help in restoring my HHR SS.

 

First off but probably not the cause, have you replaced the cabin air filter?
check to ensure the hvac module connection is firmly in place

 

My first guess is the fan switch has got fried. Maybe the filter has collapsed into the fan or debris bypassed the filter. Maybe the fan is dying.
Anybody been doing anything in the glovebox or waterfall area?

 

My guess would be that the mode door was stuck. I’ll bet it was actually blowing between 2 modes like dash vent/ defrost vent.
My old Dodge truck does this a lot. I usually hear a small “thunk” noise from the dash when the door releases.

 

I will check the cabin air filter and the area to insure all is good. Thanks.

 

A member recently found that the drains under the cowl were clogged causing water intrusion on the filter. I never gave the drains a second thought, they are just a blank spot in the line between the fender and the body at the lowest point.

 

I vote on the mode door being sticky. Could be a slightly warped duck.

 

Warped duck ? 🦆

Or duct.

 

Howard the Duck is a little warped.

 

Daffy was a little Looney Tunes