Funny Interfearence in Subwoofer

[Son of a Gun]

Howdy, When I bought my '88 ranger it came rigged up with an "impact urban Audio works" woofer. And a "Cadance ultradrive 4000" amp. (and an aftermarket radio of course). Now when the engine is not running it sounds great, however if the engine is running, it gives of a high pitched whine/hum, and it increases as the engine is throttled up. Sounding something almost like a turbo. On occation it silenced for a few moments. I gave some pics to see the set up. Let me know if you want a shot of anything specific. It all sits behind the seats mostly on carpet. You can see the portion under the subwoofer where there is no carpet. I tried throwing a t shirt under it to see if it made a difference, but it didn't. Any Ideas? Thanks

 

[Nordren]

Almost sounds like it could be a struggle for your alternator. It'll run off the reserve from the battery while it's off. I have a similar problem in mine an I think it's that. What size is your alt? An what amperage is required to run the amp

 

[drsvox]

Where is it grounded? Most likely that's what's causing the interference. The amp should be specific about wire gauge and max length in order to be properly grounded. If it's easy to get to, you could try running a new ground wire straight to battery neg to test and see if that clears the problem.

 

[AgPete139]

Use a 3' ground with a solid connection. It's interference with your alternator. How do you have your power wires run? ideally, you don't want them bunched up. Also, check your REM and power connections at the amp. These all contribute to that whine you receive when you step on the throttle.

 

[adsm08]

The battery will pickup the slack in the engine is running too. The Focus ST has a bigger battery than a regular Focus because it has an upgraded audio system.

I don't know much about subs and amps and such, but that sounds like classic RFI to me.

Disable the alternator and start it up, see if the noise is gone.

If it is, great, noisy alternator, bad rectifier, get a new one.

If it's still there you probably need a new coil.