radio interference

Post by **scouse** » 20 Nov 2006, 10:34

Just re-fitted my radio cassette which is dash mounted. All I have done is changed the aerial and the speaakers/speaker wires.

I am getting a lot of whine from the engine, and when i put on the wipers. This never happened before with the old set up. The radio is a standard radio cassstte with a single live/negative and left/right speakers.

I can't understand why there may be a need for suppressors as none were fitted before.

Any suggestions/tips please.

Thanks

Scouse

Post by **Mocki** » 20 Nov 2006, 12:10

most likely cause is a bad earth connection on the antenna, and if that is 100% good, a poor neg connection either to the speakers or to the radio itself.....

incorrect antenna length can also cause this, but i doubt it in your case....

Post by **scouse** » 20 Nov 2006, 17:25

Thanks Mocki will check everything tommorrow

Scouse

Post by **scouse** » 23 Nov 2006, 18:03

Checked the aerial seems to be connected to the bodywork ok. Discovered that the original earth spade on the radio was u/s, and the radio was self earthing as soon as it touched the metal radio cage fitted to the dash.
I have fed a separate earth to the body, and still get the interference when the engine is running. Also get feed back from the wiper motor!

Could it be a knackered radio?

Scouse

Post by ju » 23 Nov 2006, 20:29

I had this problem with an old mini i had a long time ago, and it was resolved by a friend who fitted some sort of shielding around the aerial wire. Sorry i can't give any more info than that, but i do know it was reradily available from motor factors at the time.

Ju

Post by **Dan Wood** » 23 Nov 2006, 20:33

Does it do it when playing a cassette, or only when using the radio? Is FM affected as badly as MW ?

As M0CKI said, most likely a bad earth, but it could also be that the radio is sensitive to a 'noisy' supply too. Dirty contacts in wiper motor will put nasty spikes on the supply to the radio, which it is supposed to ignore.

You can get after market filters that should help, but you need to to fit them as close to the radio as you can.

Post by **ghost123uk** » 30 Nov 2006, 12:26

As Dan says, the first thing to establish is whether it does it when playing a cassette or just when using the radio ?

Filters at the head unit end of things often have little effect if the interference is on the radio only.

If it is doing it on both audio sources then a filter capacitor is easily fitted across the 2 wires on the wiper motor and will cure that. Available for £2 from most motoring shops.

The alternator whine is likely a different matter though.
You can fit an appropriate filter capacitor on that too, also available from the motoring shop, but usually it is caused by what is known as an "earth loop". That is multiple earths, going to different bits of the body work from the same audio source. This often occurs when you are using an external amp on your audio system. Are you ?

Good practice is to keep the earth wire on the head unit as short as possible.

Post by **scouse** » 04 Dec 2006, 17:47

Thanks a lot for the responses.

The van is currently away at the moment. On its return I will give it another go.

Ghost123uk no external amp fitted. the system is too basic. Have decided to replace the radio as it must be as old as the van!

Regards

Scouse

Post by **OLD ONE** » 04 Dec 2006, 18:13

And the answer is..... If it ain't broke. don't fix it

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