I just had a repair on tires, wheel bearing, and front bumper from my dealer recently. Then a week after, while I was driving for 80 m/h on highway, audio volume just goes down by itself!

what's happening!

 

The dealer must have reversed the polarity when they put the wheel bearings on.

LOL jk, thats odd. im curious to see what the issue is, too.

 

Some of these systems have a speed sensitive volume, but it shouldn't go down at speed I wouldn't think........ This can be enabled/disabled if you have it.... check your manual.

Mine has it but I don't use it and really don't know how it reacts and don't remember where the "enable/disable" was located (Driver's settings in the DIC, or preference settings in the stereo)

 

I believe it's in the preference settings in the stereo. Had that in my Impala, and the only time it went down was when the speed went down..... Or if I really gunned it to pass someone, the volume would go up and then back down when the engine quieted down a bit. Your situation doesn't sound quite right, though, it's really odd......

 

You have some kind of malfunction going on there. Some have mentioned SDV (Speed Dependent Volume) like my 2005 GTO has but, as far as I know, HHR's don't have that. That and the fact that, as mentioned, the volume would go up as speed increased not down.....

 

My HHR does have it, ('07 "premium sound system" from the factory) I just don't use it..... and yeah volume shouldn't decrease with speed. (unless there was a great sounding V8 under the hood )

 

It is called (SCV) Speed Compensated Volume. There are 4 settings, Off, Low, Med, or High. On my 09 manual, user instructions begin on page 3-65.

 

Ours is an 06 with the base stereo. It doesn't have it.

 

Could be a stuck steering wheel control or a short in the clock spring or contacts (I don't know which is used in the HHR) in the steering wheel.