Causes of FM Radio Interfence on Older Diesel Car?

Question

For the last 3-4 weeks I've had very poor FM reception.

The audio is fine when the engine is off, and at its worst when the engine is at idle. Raising the revs gives a cleaner sound out of the radio.

The interference is all cracks / hiss / pops, and seems to bear no relation to either engine or road speed.

The car is a 2001 Skodas Octavia and the engine is the 1.9 TDI 110, which uses a Bosch VP37 injector pump - not one of the more recent PD or even later CR diesels.

Headunit is an aftermarket Sony XAV-601BT - but it has been in the car for well over a year without these issues.

Any clues as to where to look first?

Thanks!

Dave Plowman (News) · Accepted Answer

Check the ground connection to the radio, and the ground connection at the aerial end.

Adrian C · Answer

Check the relevant fuse in the fusebox isn't worming its way out of the contacts from vibration. Mine popped it's way out leaving my radio dead. Probably didn't like my music tastes.

If you raise the revs a bit so it's clean, then put the headlights & rear heater on - do the faults come back? How's the battery? I note on your Briskoda post you are also having fault lights from TCS / ABS.

Finally, I've had two Sony car decks fail on me after a year of use. Radio reception went completely, but CD / Minidisc fine....

David · Answer

Have you recently installed a dash cam, car dvr ? Many of these devices I've had created enormous interference on FM. David

Ian Riches · Answer

Nope.  Nothing electrical/electronic has been touched on the car since  the headunit was installed. Ian

Lee · Answer

Although you say that it's not related to engine speed, I'd still be  inclined to stick a 'scope on the alternator output...

alan_m · Answer

Those mini 5V USB voltage converters that fit into the cigar  lighter/power socket can cause a lot of FM interference

David · Answer

I have had cameras that did not even need to be plugged in create  interference, and without the 5v USB supply plugged in either... The last one had a 6v supply on a standard mini USB connector. David

Derek · Answer

The way FM works says it cannot suffer power spike interference. I would be far more inclined to go for a dodgy connection to the radio or a faulty head unit itself. Take the radio out of the car and fire it up on a bench supply.

Duncan Wood · Answer

Given basic physics, almost any level of Electronic engineering & trial &   error say you're wrong there I've no idea why you'd think that.

Causes of FM Radio Interfence on Older Diesel Car?

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