Alternator noise

[Oblin Goblin]

Today I was replacing my wiper motor and I forgot to disconnect the battery cables before I started. While I was installing the new motor something shorted out and I blew a fusible link at the starter and I melted a wire. The wire that melted goes from a junction mounted to the body above and behind the middle of the engine to a block that bolts onto one of the wiper motor mounting bolts. I have no idea what the block is for, maybe someone can tell me. There are 2 posts with a wire going to each and its on a bracket that bolts on with the wiper motor bolt. No other wires appear to have been damaged.

Anyway, I replaced the fusible link and the melted wire and all is well except now I’m getting an alternator wine in my speakers. I’m also getting and irregular static type noise that doesn’t seem effected by engine RPM or anything else. I don’t get either noise with the engine off. Both noises only come from my rear 4 speakers, which are operated by an amp. There’s no noise coming from the front speakers, which are operated directly by the receiver. Both noises go away when I unplug the RCA inputs from the amp. I never got any noise before today. What could have happened? I’m a little afraid something might have been damaged when the wires shorted out. Or maybe the noise indicates something faulty in my wire patching. What do you think?
Thanks
.

 

[Prembird]

Well you have trouble shooted it down to having to due with the amp... So with the info you have given the first thing i would do would be to relocate the ground... The whine your hearing is a ground loop problem.. This can be caused by many different things... But relocate your ground and see if that helps in the matter...Now there could be one other possiablity... You fryed your rca outputs a little and is causing this but i do not believe this is the case..

 

[Greg72]

Prems got it right (of course! /forums/images/icons/cool.gif)....

The "alternator whine" is caused by a difference in ground potential bewteen the various components in the audio system. My guess is that your head unit is not grounded to the same spot as your amp(s).

Try consolidating all your grounds (related to the stereo)....make sure it's a nice clean, bare metal ground spot....and don't run them all directly to the negative side of the battery! Believe it or not, that is a very "noisy" place to connect your ground wires.....

 

[Oblin Goblin]

Fixed it! I discovered that my engine to body ground strap was in sorry shape. I replaced it and all is well.