Never heard a sound like that on an HHR. The only time I recall hearing anything remote like that was on my 90 Ranger but the sound was coming from the compressor.

 

With the vehicle off, blow air through the condenser. If you can replicate a similar sound, you have loose fins or possibly debris stuck in the fins.

 

Finally found the problem. Changed out the pressure switch anyways since I had to get in there. On my SS the inter cooler piping was changed to an aftermarket which is apparently bigger than stock. There is a vacuum tube and sensor at the bottom before entering into the inter cooler which is pushed tight against the factory pressure switch plug and has rubbed a wire bare. We separated the wires and siliconed it up and it works great now. Will fix it the right way later when I take off the front end to install new. Thanks for all the help.