Whistle from Speakers - Ground Loop

[axekick]

I've been trying to track down this ground loop in my sound system. It'S A 2005 Suburban with an aftermarket deck and steering wheel control module. I even got a new deck hoping the problem was internal to it but it is exactly the same. I think I figured out that if I move certain wires around in the harness it affects it. I think there's a short behind the deck a little too deep in the dash for me to access. Does anyone ever grind or drill the couple rivets on the panel behind the stereo/AC controller to access the harness back there? Is there a way to get the whole harness out?

 

[Joseph Garcia]

The only ground loops that I've 'heard' are low frequency sounds and not a whistle.

When you changed out the head unit, did you do anything other than plug in the head unit and steering wheel interface unit connectors, and was it simply plug and play with no modifications?

Also, try connecting a piece of wire to a good ground connection and touch the other end of the wire to the metal chassis of the head unit with the head unit turned on. Does your ground loop sound change?

 

[axekick]

I've tried that. It doesn't make a difference. The whistle seems to come from all the speakers and changes pitch with RPM. I ordered a new steering wheel control module too and it should be here today. When it gets here, I'll wire the harness to the stereo per the instructions. Then it just plugs into the factory harness. BTW this is a factory Bose system and it's using the factory amp.

 

[SpareParts]

Maybe it's alternator whine you are hearing? Does it do it not running?

 

[justirv]

I've tried that. It doesn't make a difference. The whistle seems to come from all the speakers and changes pitch with RPM. I ordered a new steering wheel control module too and it should be here today. When it gets here, I'll wire the harness to the stereo per the instructions. Then it just plugs into the factory harness. BTW this is a factory Bose system and it's using the factory amp.

Check to see if your hood ground strap is intact. There should be one attached to the top of the firewall. The (grounded) hood will provide additional (EMI/RFI) shielding, which would coincide with the change in RPM. Then look into the Big 3 (or 4) grounding solution, many electrical problems can be solved with that.

 

[axekick]

It does not whine when the engine isn't running. I did change the alternator. I also found the ground strap to the hood missing and added a new one. I was pretty sure I'd found the problem when I saw that but adding it made no difference.

Wriggling wires around behind the deck does make a difference, and I peeled back the tape on the ones that seem to be the culprit but didn't see any bare wires. I think they were blue and black and twisted together with some kind of bare wire twisted up with them and wrapped with aluminum foil and plastic. I just don't think I can't get far enough back in the harness to find the problem. There are rivets on the dash preventing me from removing the part that's in the way. I'll get some pics when I swap in the new deck and steering wheel control harness.