Re Rover 75 radio interference

Thanks to contributors Tim Kemp and Matt Wilson

In my original posting I wrote: Rover 75s suffer from radio interference. On the FM band this is radiated by the wiring and is generated by the car computer. Can anyone describe how to get at this unit so I can try some RF decoupling.

On Long Wave there is interference that I suspect is related to the fuel pump (because its there as you activate the ignition but without even starting the car). Can anyone describe how to get to this unit or associated cables.

In both cases, if the radio signal is strong enough its OK, but radio reception is very poor in relative terms. All 75s I've assessed are the same except diesels.

Tim Replied: My V6 with premium sound (H-K) was faultless audio wise.

Matt Replied: Surely this should be fixed by the dealer as it is in breach of the Automotive Directive 95/54/EC for electronics in vehicles.

Long Wave is OK on strong stations but please tell me if RTE R1 is OK in the south east on 252kHz on yours when engine is running.

Thats an interesting point about 95/54/EC however does this just cover radiated external emissions or does it include effects within the vehicle? This problem is one that only affects the cars own radio. I know that the problem on FM is caused by the car computer. I used a scanner to show that the interfering signals stop being radiated 1 minute after all car electrics are turned off. A Rover source confirmed that the computer closes down 1 minute after switch off. On FM the effect is that signals are present on a number of specific frequencies on the FM band. Most of these spurious signals emitted by the computer are small so they are swamped by the wanted radio stationand everything sounds OK, but in some cases (eg 96MHz) the signal is quite large and causes audio disturbance to a co-incident station (eg Radio Cambridgeshire) even when the station signal is reasonable. It is not an antenna fault because the radio can be seen to receive distant stations quite well if their frequency is not co-incident with one of these spurious signals. At the time I first investigated this I confirmed the problem with several other 75s.

There are also strange effects on MW. In this case low strength stations are often accompanied by a whistle that slowly changes pitch. This has been confirmed (by the local Rover dealer) to occur in other 75s. Sometimes, application of the footbreak momentarily removes or reduces the whistle!!! - This sounds like an earthing problem.

Perhaps Rover lost their radio specialist at the time of this design!!

So, back to my original question. How do I get to the computer module and the petrol pump? As a Chartered radio engineer myself I just may be able to sort it (but don't hold your breath !!!)

Thanks for help

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Chris L
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