Tach, MPG and Temp Gauges don't work

[ACHTUNG]

I checked all my fuses and they are fine. My Tack and MPG gauges never work however my temp gauge will intermitely work (it doesn't work 99% of the time).

what should I check to get them to work?

[jlevie]

Bad batteries in the SI board, or a bad SI board, or a failuure of the fuse that supplies un-switched power to the SI board can cause this. In rare cases this particular set of faults can be caused by a failure within the DME and a bad connection between the cluster main PCB and the temp gauge.

[mattdk318i]

the same is happening with mine. The temp is pegged out and the tach only works part of the time

[ACHTUNG]

Bad batteries in the SI board, or a bad SI board, or a failuure of the fuse that supplies un-switched power to the SI board can cause this. In rare cases this particular set of faults can be caused by a failure within the DME and a bad connection between the cluster main PCB and the temp gauge.

crap

[mattdk318i]

i took my cluster out and checked the connections. But to no avail. I think im going to try to replace the batteries next. Does radio shack sell a similar battery?

[mattdk318i]

Alright, Im bumping this because it happening again. This time with the M50. The Temp gauge doesnt work at all, But sometimes pegs to all the way hot when i turn the ignition on. The tach doesnt work either
Im sure the wiring is correct, Because its doing the same exact thing it did with the M20.
I know that Violet and Brown is the temp and black is the Tach. I did replace the temp sensor on the M50 with the M20 one.
At this point im really ticked. Because Im not driving my M50 without temp and tach. And its extremely irritating to be out of the know with something that important.
If i cant figure it out soon ill throw a cheap 1 wire temp gauge from a auto store...........

***I should add that i took a volt meter to the SI batteries and it was reading 2.89 volts on both of them.

[mattdk318i]

bump, Im up to suggestions and Rhetorical questions. Send anything my way. Ive exhausted everything i know to do.

[atomic]

wild guess here and not sure if it would have that effect on it but have you checked the ground nuts on the back side if the cluster ?

[mattdk318i]

i have, The tach now works. So now ive got to figure out why the temp gauge pegs to hot as soon as the ignition is on.

[mattdk318i]

Well, i guess driving is the best remedy. I was rolling over some speed bumps and the temp gauge started working, However it would flicker from mid to hot and the BRAKE LINING light got brighter and dimmer as it flickered
WTF? are they connected somewhere?

[DaveSmed]

SI board.

[mattdk318i]

hmm, we checked the board and it seems to be a replacement. The local BMW garage said its what they use for replacements as well.
So we checked the batteries as previously stated and they were at 2.89 volts a piece(3V new)

[DaveSmed]

Hmm, connector between the SI board and the cluster main board OK? The temp gauge runs through the SI board, the brake lining light system is controlled completely by the SI board, and it has connections to the tach and economy gauge.

Pull the thing out and reassemble the cluster. Your temp gauge will be dead (should read cold) but your other gauges should work. If this is the case, it is possible to jumper the SI board connector and eliminate it.

[UNHCLL]

The main circuit board is cracked/old/aged.

This is common on these cars as they get older.
A flickering temp guage that fluctuates way more wildly than the engine temp can is an indicator. If it peg's out at full hot, then after a tap/slam on the dash or a speed bump, bounces back down again... it's a bad main board. You can try tightening the grounding nut on the back of the temp guage, but it likely won't work.

YMMV.
-C

[mattdk318i]

thanks for your help guys. Im going to see about locating another VDO SI board. My cabrio has 102K and id rather not just swap in another cluster with tons more mileage(yes i know how to run them back)