C240 98/S AM radio interference

[proteo]

Hope some one can shed some light on this.. My Blaupunkt radio works fine, except in AM where I get feedback from engine revs etc. I tried the radio in an Eclass and it works fine, both cars have the aerial integrated on the rear window heater. I tried an alpine radio in the class thats fine too?? Seems like a strange aerial related problem?? also tried an inline aerial booster but no joy. Help pls..

 

[Arnie]

The problem is most likely to be caused by the metal shields on your spark-plug connectors (you should have them, if you have original leads), being corroded and/or not touching properly the metal (earth) of the spark-plug bore of the engine; such that they do not provide an effective shield against radiated RF interference. (The first radio transmissions were done with a spark machine)

The other possible source could be a problem with RFI filter on your alternator, which is supposed to absorb conducted RF interference. You could buy another one (small capacitor device), which you connect between the output lead of the alternator and a good chassis ground.

 

[OlafMaxwell]

have the same problem but from the brakes, when you press the brake pedal you get a whine.

A company the size of Mercedes were unable to fix it.

No wonder they are having to buy back cars that are having brake failure. They could not design a wheelbarrow.

 

[proteo]

Arnie - appreciate the info. I'll check out the spark leads / shielding, earthing etc and the suppressor on the alternator. Thanks.

 

[OlafMaxwell]

We used to fit suppressors/capacitors to the alternator wiring, also needed good suppressed plug leads. Crackle type interference was ignition, whine type electrical interference. Earthing needs to be good too. Keep all wiring well away from ignition system wiring.

Ariel needs to be good and also needs a good earth!!

Good luck!!