Rev Counter Operation - The Unofficial BMW M5 Messageboard (m5board.com)

dronfieldm · 23rd September 2002, 17:56

People,

How does the rev counter collect the engine speed.......

I nipped out to the local shops this lunch time and all was OK. When I drove back to work, I noticed that the rev counter wasn't reading correctly. I was travelling up a slight incline, at I guess 1800 rpm, but the gauge showed 200 rpm. When I parked up I revved the car to, say 2000 rpm, and the rev counter moved up from 200 rpm to 800 rpm.

This is very weird !! Car drives fine. I'll have to see what happens when I drive home. It was fine this morning.

In the "olden days" they used to feed from pulses from the coil didn't they ?

Any ideas ?

Maybe last nights earthquake has affected it !!!!

Many Thanks
Mark

Alan Archer · 24th September 2002, 01:04

hmm,

two options, gauge or control,

Firstly do the usual test....ignition off,press&hold right
hand check control button, turn on ignition, let display
test function, finally, the instruments should test.
Both speedo & rpm gauges should rise to vertical, around
85mph & 4000rpm, then return to zero.

Does this work ?

The second cause of the fault could be faulty/dead batteries
on the rear of the instrument pack...these batteries are soldered
in place but are replaceable.
I've only ever had them go on E28's but E34's are just the same,
and the results of dead batteries on E28's include no temp gauge
and erratic revs/economy read out.

Regards,

Alan Archer.

dronfieldm · 24th September 2002, 12:04

Thanks for your help Alan.

It was just as I hoped. Drove home last night and all is fine. It has been fine since. What can I say ? I'll just have to keep an eye on it.

I am definately not going mad, I did see it !!!!

Thanks
Mark