I had just driven my '09 HHR Panel two days before, and the A/C was perfect as usual (sub-40 degree air from vents). Then, on Thanksgiving, I turned it on for our return trip from the in-laws ranch, and the A/C clutch/compressor never kicked on (temperature out the vents was 80+ degrees). Today, I checked the #22 A/C fuse & the #15 relay (and re-seated the #9 diode) in the under hood fuse box, reseated the HVAC relay #30 and checked fuse #10 in the inner fuse box, and checked for loose or frayed wiring to the A/C clutch as well. The control panel switch seems fine, and when I dial it for heat, there is heat, but still the A/C clutch never engages. What should I check for next?
P.S. my car problems come in threes, it seems. I had tried to fix my wife's Cobalt's "sinking brakes" problem three weeks ago, replacing pads/rotors in front (throwing my back out in the process...keeping me from doing the rear drums), so it still is parked. Three days ago, she tried to start her '98 GMC pickup (after faultless operation for many months), and the single "clunk" from the starter solenoid showed me it was time for a new starter (voltage, etc, all good), but again, my bad back and the sandy parking spot she had chosen, will make that simple fix harder). So, now she was driving the HHR, while waiting for her vehicles....I'm not gonna let her jinx my '04 2500HD, or we'll be walking (OK, maybe the inoperative HHR A/C isn't immediately life-threatening, but it still gets warm in Texas in November!).

 

What was the coolant temp?

 

Didn't check that, should've. Will check it later and get back with you after roadtest.

 

Are there any CEL codes, a P0128 will turn off the A/C .

 

Drove it 48 miles,avg. speed was 56 mph, and stopped for gas midway. Ambient air temp was 65 degrees; highest temp while driving 232 then dropped to 222-225, and 244 before dropping to 232 degrees when at home (idling in drive for ten minutes). My scanner only showed an unrelated code, a P0446 (set on Chevrolet Enhanced), following my wife trying to force-feed the HHR at a fill-up Monday. I had it inspected the next day, with a full pass. I replaced the vent solenoid two years ago, and hadn't set a code until she did, go figure.

 

Those temperatures are very high, seeing as the thermostat should be opening at about 180 degrees. Have you noticed any coolant in the oil? Possibly a head gasket issue.
What coolant are you using, Dexcool 50/50 mix is the highly recommended solution, and changed every 5 years, yes it had a shelve life . Just 5 years.
your problem could also be balance shaft chain broke, or the water pump impeller isn’t turning.

 

I don't see oil/coolant mixture, but the coolant is super low. Maybe if I change the thermostat (sensor also?) before I get a P0128, then I can reset the system? It's been 6-7 years since a Dexcool top-up or change (I retired five years ago, so my neglected one-time daily driver HHR has only been driven 2.5k miles since, now its at 167k).

 

If it is very low in the bottle I doubt there is much under the pressure cap.
As Oldblue stated Dexcool has a 5 year shelf life, whether it is used or not. If it got up to 242F it is probably chemically destroyed.

 

Thanks. I'll start a fix this weekend. Being old school, I've had much hotter coolant before, and never a problem shutting off electrical devices because of it. Wasn't covered in my GM Tech school classes in 1971.

 

No it would not have been, the Ecotec engines being aluminium, they don’t like high temperatures.
then only thermostat they like is the AC Delco 131-158 180 degrees F , others don’t open within the parameters the computer is looking for.