Instrument Pack Intermittent Failure - The Unofficial BMW M5 Messageboard (m5board.com)

FinalEditionE34M5 · 5th February 2009, 20:06

Evening All,

Here's one I haven't experienced before - been driving Project Calypso (yes in the snow) up to Milton Keynes and back this week whilst my 540i is unwell.

Car is running very well indeed and sits on the H&r Springs nicely poised, with awesome power from the 'small' brakes now that we have new discs and DS3000 PAds on.

One thing - the Instrument pack is intermittently-failing - sometimes it works fine, on other occasions, the speedo and rev counter read 'very low' - and by that I mean they become 'lazy' - at circa 70Mph in 5th the car is reading 20 Mph and 1,250rpm !

- I only know the speed the car's travelling-at by quickly re-setting the average speed on the fuel computer for an instantaneous speed check......

Any ideas ?- Instrument Pack need replacing.........? - or is this an easy fix ?

BTW, all other parts are working perfectly all the time - Fuel Guage, Temp Guage, and Mileometer...

legacy260 · 5th February 2009, 20:14

Loose cables or maybe moisture in the connections??

JohnR · 5th February 2009, 20:41

Mine did this when the battery was dying & the Alt was going out.
Hope this helps!!
John

stevie sam · 5th February 2009, 22:13

Hi Terry, long time no speak how are you, Is project Calypso gonna be ready to track day this year?

Tomba · 5th February 2009, 23:58

Maybe time to change the capacitors on the circuit board...

Troubleshooting instrument problems

If you can, swap it with another one and see if its instrument cluster specific or car.

FinalEditionE34M5 · 6th February 2009, 02:34

Thanks for the suggestions - will check those - the battery in the car is brand new so it shoudn't be power - related.

Stevie Sam - Calypso is ready for 2009 ! - Will post a full update on my original thread on the car soon.

Two track days booked for this month - starting with this Sunday at Snetterton..... We'll see how she goes..

Baddie · 7th February 2009, 23:46

Hi Mate

I read somewhere that there's a small rechargeable battery soldered to the circuit board to provide power for the service indicator when the main car battery is disconnected. It is supposed to last 6 years. The picture I saw indicated a 1.5V type like an AA cell. If it dies or leaks it can play havoc with your display, but is relatively easy to replace once the display panel is removed.

If this is total rubbish can someone please correct me and save a job?

Best of luck, Anwar

stedes · 8th February 2009, 07:20

Hey Baddie,

Not heard of this one before. Own 1989 E34 520i (from new) and 1991 M5 and I haven't had to replace the battery on either car from new. Could it be that it fails and leaks rather than discharges?

Baddie · 11th February 2009, 14:15

Yes, seems likely. I've never heard of anything like this as a maintenance item before but then we're keeping cars beyond their planned lifespan. Think I read in the Haynes manual, but I don't take everything in there as gospel.

BURTON · 11th February 2009, 14:30

Have you tried relays? or Fuses?