Weird radio problem

[starman]

I'm afraid this relates to our car rather than our boat but hopefully one of CWF's gurus might be able to help all the same. We have a Citroen C3 with one of those roof mounted amplified aerials for its standard fit radio/cd..

Normally on local trips it works fine on AM & FM but several times now when we go further afield a strange whistling starts to intrude which quickly becomes a cacophony of white noise style interference on all stations. Turn the volume up really loud on you can still hear the original station under the racket (just).

This then persists even when we return home but the weird thing is that after a few days the radio reverts to working fine again! This has happened two or three times in the last couple of weeks on different journeys and after different periods on the road. During all this, by the way, the CD will work perfectly.

My pure guess is that it's an aerial fault but as getting at this involves removing some of the roof lining (thank you Citroen) I don't want to replace it without being certain.

Anyone got any ideas?

[blodger]

I'm afraid this relates to our car rather than our boat but hopefully one of CWF's gurus might be able to help all the same. We have a Citroen C3 with one of those roof mounted amplified aerials for its standard fit radio/cd..

Normally on local trips it works fine on AM & FM but several times now when we go further afield a strange whistling starts to intrude which quickly becomes a cacophony of white noise style interference on all stations. Turn the volume up really loud on you can still hear the original station under the racket (just).

This then persists even when we return home but the weird thing is that after a few days the radio reverts to working fine again! This has happened two or three times in the last couple of weeks on different journeys and after different periods on the road. During all this, by the way, the CD will work perfectly.

My pure guess is that it's an aerial fault but as getting at this involves removing some of the roof lining (thank you Citroen) I don't want to replace it without being certain.

Anyone got any ideas?

Another possibility is alternator 'noise'?

[bottle]

I do not think it is the aerial, it sounds (pun) more like an electrical interference noise, perhaps something is 'breaking down' when it heats up, bad connection somewhere, maybe a suppressor (do they still fit suppressors).

 

Good luck in finding it, I wouldn't know where to start.

[johnjo]

Can't help with what's causing the actual problem, but I would have thought that an aerial fault would have remained consistent.

[Arnot]

Anyone got any ideas?

It sounds like the symptoms of the aerial earth connection to the inside of the roof starting to corrode. What happens is that as long as it is damp the connection is good enough but as the car is used for longer journeys and thus warmed up, the corrosion drys and becomes a resistance. At this stage any current flowing through it creates electrical noise which is reproduced through the radio receiver.

 

The solution is to drop the roof lining, remove the aerial, clean up the aerial lead and the inside of the roof, coat them with vaseline and reassemble.

 

This is only one of the possible reasons (but fits the description of the symptoms), the bummer is that you will only really know if it was this if the remedy cures the fault...

 

Good luck

 

Regards

 

Arnot

[rjasmith]

I know it's a Citroen fitted radio but can you get at the aerial plug at the back of the radio at all? If you can and before you attack the headlining perhaps you can try a substitute radio aerial of some sort - even a bit of wire to hang out of a window!

 

If the fault goes away then it was the aerial but it could easily be an intermittent fault in the radio itself, in all sorts of places!!

 

Although I agree with Arnot's corrosion possibility, would a C3 be old enough to have done this - anything's possible I suppose but our old 98 Saxo roof aerial still works like a charm!

 

Richard

[RobinJ]

It sounds like the symptoms of the aerial earth connection to the inside of the roof starting to corrode. What happens is that as long as it is damp the connection is good enough but as the car is used for longer journeys and thus warmed up, the corrosion drys and becomes a resistance. At this stage any current flowing through it creates electrical noise which is reproduced through the radio receiver.

 

The solution is to drop the roof lining, remove the aerial, clean up the aerial lead and the inside of the roof, coat them with vaseline and reassemble.

 

This is only one of the possible reasons (but fits the description of the symptoms), the bummer is that you will only really know if it was this if the remedy cures the fault...

Similar idea, has corrosion set in, damp is making it work, longer the journey the more it dries out, more interference?

[starman]

Thanks for all the info. I finally pulled the radio unit out - no easy job; this is a Citroen -- and the interference problem doesn't disappear when trying a temporary aerial so it looks like it's a fault in the unit rather than the aerial.

I think this is probably the better option. A brief prod around in the vicinity of the roof aerial suggests that this would be impossible to get at without tearing out half the headlining and you can never put this back tidily.

To be honest, this is typical Citroen C3. If you want a car on which you can do even minimal amounts of maintenance then don't buy one of these - changing the nearside headlamp bulb took me two hours. A replacement radio will have to be coded into the car's main management system (it doesn't have one of those four digit codes but one that has to be put in via a computer at - guess where - the dealer.) But then the same is true of most current cars I guess.

[aread2]

Thanks for all the info. I finally pulled the radio unit out - no easy job; this is a Citroen -- and the interference problem doesn't disappear when trying a temporary aerial so it looks like it's a fault in the unit rather than the aerial.

I think this is probably the better option. A brief prod around in the vicinity of the roof aerial suggests that this would be impossible to get at without tearing out half the headlining and you can never put this back tidily.

To be honest, this is typical Citroen C3. If you want a car on which you can do even minimal amounts of maintenance then don't buy one of these - changing the nearside headlamp bulb took me two hours. A replacement radio will have to be coded into the car's main management system (it doesn't have one of those four digit codes but one that has to be put in via a computer at - guess where - the dealer.) But then the same is true of most current cars I guess.

 

Yes, typical of modern small cars. It took me ages to change the headlight bulb on my C3 pluriel, and then I got it upside down. Left it like that as I couldn't face taking it out again. I imagine a larger car would have more room for access. Most modern cars have the radio communicating with the engine management system. Presumably more secure than just a four digit code.