Rev Counter not working

[deadmic]

Hi,

I have a 1989 316, and have just noticed that the Rev counter has stopped working?? Car runs and drives ok (no erratic idle or misfires - so coil should be ok)

Bad connection, terminal clean required or something in the engine bay ?

Dash is powered, other lights and gauges are working

Any ideas what have caused the issue?

[Brianmoooore]

Dash is powered, other lights and gauges are working

Including the SI LEDs?
Any work done to the car lately?
Coil and associated bits have nothing to do with rev. counter, BTW.

[Contours]

I noticed on my 316i of the same vintage that the rev counter and Mpg gauge didn't work when the SI batteries were gone all right. I found though at the time that disconnecting and reconnecting the battery a number of times eventually resurrected the rev counter.

[Brianmoooore]

I noticed on my 316i of the same vintage that the rev counter and Mpg gauge didn't work when the SI batteries were gone all right. I found though at the time that disconnecting and reconnecting the battery a number of times eventually resurrected the rev counter.

The batteries will now be slowly leaking a corrosive liquid over the SI board. Eventually it will penetrate the protective lacquer covering the copper tracks and start attacking this copper, resulting in a written off board.
Batteries are easily and cheaply replaced by anyone who knows which end of a soldering iron gets hot.

[deadmic]

Team, After some investigation, the problem has now been identified as a bad connection on fuse 21 (10amp) in the fuse box cluster, which is also for the interior/boot/radio??. electrical contact cleaner and reseating the fuse. Why this had effected the rev counter, i am not sure. But the rev counter now works..

[Brianmoooore]

Never seen a "bad connection" yet in an E30 fusebox that can be cured by contact cleaner. The occasional cracked solder joint, and an unscrewed connection for the main power feed, maybe, but not a tarnished connection.
Fuse 21 provides the charging current for the SI board batteries in the instrument cluster, but, in good order, they should be capable of supporting the board for a few years without charging.
The fact that the rev. counter failed after a short period shows that they are dead, and should be changed ASAP, before they leak.

[arrisbmw]

read post. is it a difficult job to access the S.I/ rev counter batteries. I assume removal of the instrument cluster. ?

[Cloggy Saint]

SI board can only be accessed from the back of the cluster, so it has to come out.

[Brianmoooore]

Cluster out (no need to remove steering wheel, whatever you may have read elsewhere), pull coding plug from lower right front corner, remove all the larger cross head screws from the back, carefully pull the front from the back, DON'T lay the dials needles down and damage them.
SI board is in the front part, held in by a single screw in the middle, holding white plastic bracket in place. Bracket also holds a small black piece of plastic in place, which is either plain or has 'check' on it, depending on whether your car has a whole engine or two thirds of one. Make sure you don't lose this piece or only notice its missing after the cluster is back in the car.
Board just slides out, with the two batteries in the middle. Two types of battery, and must be replaced with the same type.

[ChrisHC]

Picture guide to removing the instrument cluster HERE

[arrisbmw]

ha ha. loving the engine quote.

thank for the info. where can you buy the batteries ?

[Brianmoooore]

where can you buy the batteries ?

CPC, although they have tag ends, instead of the correct pins, so need to be fitted with two 10mm lengths of wire.