I have a JVC KW-790 indash head unit in a 2006 2.4L HHR LT.. How do i get the alternator whine out of it?? Is this a common problem in the HHR??

 

Double check all grounding.. Just for a test find a bare metal spot on the chassis or the bolt near the fuse panel under the center console --touch a wire from there to the body of the HU --see if the whine goes away... If it does you can just add that wire --if not--could possibly have a bad HU .

If you have a Digital VOM --- measure in the ohm mode from the chassis to the body of the head unit-- should be less than 1 ohm.. You can also use the DC volt setting and test from the harness ground to the bolt/chassis ground while the unit is on and can hear the whine.. This should measure less than .250 Vdc or 250 millivolts... If not-- then you do have a grounding issue.

 

I have the same problem with mine. I have an Alpine cda-9887. It was first grounded thru the factory harness. Then I grounded it directly to the amps ground, still have noise. The amp is grounded to the factory point in the hatch. Ive had 2 seperate radios and both had issues.

 

I have this problem too. I have tried everything and can't get rid of it.
I think it is a long standing problem.