1991 535im --- Speedometer and Radio

[Stewart E]

Hey guys I have not posted in awhile but car running great except the speedometer jumps... sometimes does not work at all.

I know that I may need to replace speed sensor on diff.

But I have a twist to it (the problem that is) if speedometer is not working and I am driving and have radio on I can hear an increase in volume (power) if speedometer starts to work.

Makes me think it may capacitor issue in cluster but why would radio go louder (fusible link) ?

Anyone has ideas...

Thank you in advance.....

Stew

[Ferret]

Hey guys I have not posted in awhile but car running great except the speedometer jumps... sometimes does not work at all.

I know that I may need to replace speed sensor on diff.

But I have a twist to it (the problem that is) if speedometer is not working and I am driving and have radio on I can hear an increase in volume (power) if speedometer starts to work.

Makes me think it may capacitor issue in cluster but why would radio go louder (fusible link) ?

Anyone has ideas...

Thank you in advance.....

Stew

Probably the fusible link...

As the link closes up, the resistance drops, meaning your voltage goes up - which makes the speedo start working and your radio get louder due to the voltage boost?

It wouldnt have to be much of a voltage swing either for that to happen if the radio's old and analogue stabilised internally.

[DaveVoorhis]

Didn't some of the BMW radios have speed sensitive volume? Most touring motorcycles with sound systems have this, and I know some cars do. Maybe BMW is one of them?

[Ferret]

Didn't some of the BMW radios have speed sensitive volume? Most touring motorcycles with sound systems have this, and I know some cars do. Maybe BMW is one of them?

Yeah, that's interesting, I was just about to say 'but it only drops volume when the speedos not working...' before I realised what I was saying.

Sensor or wiring fault would cause that wouldnt it...?