My AC on my 2011 HHR (57,030 miles) works great, then it doesn't, then it does. Went on for weeks and finally took to shop. The did the normal checks said it was low, evac'ed the system, filled it, checked everything and $179 later I left, and the AC worked great. Next time I used the car, warm air, no COLD AT ALL. I saw the thread on the Tstat problem, but doesn't seem to apply... my gauge works fine and no code (the shop should have noticed if it showed a 128). Anyone have an idea of what's going on before I go back to the shop and rack up more expense to fix it. BTW.... I LOVE my HHR!

 

 

Welcome to the site.

AC systems don't just get low unless you have a leak. If the shop didn't repair the leaking part, then the freon will just leak down again. That may be the case here that it's leaked down enough to cause cooling issues.
I would take it back to them and have them check the freon charge.