Thread: Hissing sound coming from rear speakers.....

I have an '04 GTP Comp G with the premium factory sound system. On and off I hear a hissing sound coming from the rear speakers only, even if the sound system is OFF.
The hissing speeds up and slows down with engine speed. Weird thing is that it appears to start and stop if I hit a good bump in the road..... at least that how it seems..... I did have some work done on the AC system, condenser change, a few months ago and I believe the first time I heard it was right after that.. But now it's happening more.. Any ideas what it could be ? Thanks, and Happy Thanksgiving !!!!!

Originally Posted by dsmuts

Do you have anything hooked up to the cigarette lighter outlet or an fm modulator or anything?

Yes .. I am using a cigarette lighter power supply for a satellite radio and an FM modulator to get the satellite signal into the car radio......

Originally Posted by dsmuts

Thats probably causing your noise.

I disconnected the plug from the cigarette lighter socket, which turns off the fm modulator, but I still hear the hissing sound intermittently.....

Originally Posted by rperry435

Even if the radio is off the monsoon amp is not. It provides function for the door chime and on star. It remains on for a minute or more after doors have been closed and sometimes until the bcm goes to sleep.

I speculate if your hearing the hissing from your rears those outputs are likely taking a dump.. could be one or more solder joints on the amp board as well since u hear it over bumps

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So what do you mean by "dump" ? It seems that a good bump will cause the hising in the back to start..... sometimes it just starts on it's own ... It continue at times even after the car is stopped and the ignition and radio is OFF. The FM modulator for my satellite radio doesn't seem to have anything to do with the hiss,, since I have totally disconnected it and I can still get the hiss in the rear speakers ..... What can I check ? Can not find a ground up in the trunk where the amp is mounted ..... is there one there ? Thanks.....

Originally Posted by rperry435

He can check his ground and ohm it out but I've seen the hissing problem in many grand prixs and g6's with the monsoon amps.. He'll bose ones do it too. new amp always fixes the problem

Typically in aftermarket stuff a buzzing or whine with rpm is a ground or interference issue.

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\ Thanks guys ...... The change in the pitch of the hiss with engine speed made me think it might be a ground issue.... Also, how it can come and go with a good bump in the road mage me think that way,, but I guess that could also be a bad solder joint in the guts of the amp.... This mounted in the trunk, so if I want to check the ground before resorting to buying a new one, where is the ground and how do I check it ??? Also, if I need to buy a new amp, any recommendations as to make and model ???? Thanks .....

Thanks rperry ..... Any idea what these cost these days .....

Originally Posted by rperry435

I'm guessing but Between 150-250

When you call the dealership to get a price ask what the new part number is and search for it online that way you won't get stuck paying list price. I think some people go to rock auto.. Gmpart direct seems pretty close to my price when I compare them against my cost at work.

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Thanks again rperry !!!!! I will follow your advce and get back to the forum with how I make out .... may take a week or more,,, with the holidays and this not being a "Car Down" situation ......

Actually, the fix was an easy one ...where the wires for the left rear speaker pass thru the hole in the metal frame of the shelf under the rear windshield, one of the wires was pressing against the sharp metal edge and its insulation was actually being cut.
I moved the wire and wrapped it with electrical tape to keep it away from the metal edge and that fixed it !!!! Problem solved for next to nothing ..... It was a ground loop issue after all .....

Well, it wasn't a complete cut into the insulation, so I don't think it was a short.. That would have been bad... It was enough of a cut to allow the speaker signal to pick up noise from the car body / ground ..... Either way, so far so good... it's been weeks since I have heard the noise once I wrapped it in tape....

Originally Posted by rperry435

Awesome to hear you got it figured out. Not a ground loop though lol..thats just a plan old short if the insulation was cut and rubbing on metal.

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