Need help troubleshooting whine in speakers

[roger2]

Hi all. I'm trying to solve a mystery. Whine in speakers of my car system, even when the engine is not running. When the engine is running the whine fluctuates, pitch goes higher, when the engine RPMs increase.

This is not a new installation. The system was fine for about a year with no problems. Nothing has been changed or added.

I have already done the basic troubleshooting: I checked all connections. Grounds are all good. Swapped out the amp and the problem didn't change. Swapped out the RCA cables and no change. Removed head unit and ran a seperate ground wire to it, no change.

However I did discover how to make the whine go away. There is a 4-prong connector plugged in to the alternator - when it is un-plugged the whine goes away. (picture of the connector below)

The system has no whine when this 4-prong connector is unplugged.

When this connector is plugged in there is no whine when the key is in the "Accessory" position. But when the key is in "ON" position (with engine not running) the whine comes back. And finally, when the engine is running the whine changes with engine speed.

At this point I suspect a problem in the car electrical system and not in my head-unit or amps. But I do not know enough to go further with out some help

It is interesting that having the key in "Accessory" position yields no whine but moving it to "ON" makes the whine appear.

Any thoughts?

[I Am An Idiot]

Try this

[roger2]

Thanks I Am An Idiot for the link. There was about 200 ohms between the HU case and the RCA shields. I fixed it as shown in the web page link.

And props to Perry Babin for offering such a useful and informative web site.

And if anyone was wondering, yes my HU is a Pioneer.

Working fine now and sounding good. I missed my car system but it is back

[jol50]

Must be something in the car makes noise with the key on. It will pick up noise from anything with no RCA ground. Mine still working ok but only had two different amps on it so far. (880prs) Planning on testing more amps though so hope it holds out.

[Dan2]

well what would come on with the engine off and ignition ON??? Don't fuel injected cars have an electric fuel pump that come on before the engine starts??


Yes i must also say props to Perry for his site, my Pioneer HU gave me engine noise before i used Perry's fix

[jol50]

Most fuel pump come on and shut down if the engine is not started, but other things are on like ECU, heater fan, all the sensors for gauges/emissions/etc.