1993 e30 320i rev counter and mpg not working

Post Sun Mar 18, 2012 1:01 pm

i bought this car and the rev counter and mpg are not working...i took the clocks out and see the service indicator lighting up so assume the batterys in the clocks are ok[?]
or mabe not...

i would appriciate any help or advise..

thanks

Post Sun Mar 18, 2012 9:46 pm

any ideas??

Post Sun Mar 18, 2012 9:50 pm

Most likely fault is in the service indicator board,easiest fix is to swap in a replacement board.

Post Sun Mar 18, 2012 9:50 pm

the SI will light up even if the SI batterys are duff......

"rev counter and tacometer" = Same thing......

Post Sun Mar 18, 2012 9:54 pm

Hello - this comes up a fair bit on these boards. With me it was a blown fuse - easy thing to check anyway:

http://e30zone.net/e30zonewiki/index.php/Fuse_Box

Post Sun Mar 18, 2012 9:57 pm

ok lads..thank...i noticed the batterys are the lazer lithium batterys and look in very good condition along with the board..i know i can tell how good batterys are with out multimeter tho...

these batterys also dont have solder on them..it looks more like a rivit in the end and dont look changeable...

how much and wheres best to get a board...

thanks lads

Post Sun Mar 18, 2012 11:50 pm

The tags on the batteries are part of them. The tags are soldered to the board.
When the instrument cluster is in a working car, the batteries on the boards that use lithium cells don't do anything, and aren't used. They are solely to maintain the SI data memory when the main car battery is disconnected.
The boards that use NiCd cells work in a slightly different way. In these, parts of the board actually run from the batteries, and the main car battery constantly recharges them. Problems occur when these batteries fail, because they tend to go short circuit, and drag down the voltage that supplies some of the instruments.
The NiCd boards are much more often faulty than the lithium ones, but the only thing that I've seen wrong with a NiCd board is the batteries, or corrosion damage from batteries that have been allowed to leak. The lithium boards are more reliable, but suffer from a selection of oddball faults that are unrepairable AFAIK.

Post Mon Mar 19, 2012 12:04 am

What faults have you seen with lithium boards Brian?
I have a board with fully charged lithium cells, yet can´t reset the SI lights.... No other cluster issues though. Sound familiar?

Post Mon Mar 19, 2012 7:07 am

Mine did the same thing. it turns out that the fuse for these two parts is the same one and is known to blow. the reason the fuse blows is often that the wires under the gear stick boot get the plastic insulation worn off of them and then cause a short. Change the fuse. if it stays fixed good. if it keeps blowing check under the gear stick boot and use some electrical tape to re inuslat any bare wire. this was the case with my E30 and it has happend to other people on the forum. It is the positioniong of the wires that makes them susecptable to getting stripped and shorting. Electrical tape has kept it fixed for a few years now.

Post Mon Mar 19, 2012 7:29 am

Lads thanks very much for the help...

Is there only one fuse box on the car??under the bonnet??
As all these fuses look good...

The car had been parked up a year and car battery's totally scrap..

Post Mon Mar 19, 2012 8:45 am

A blown fuse 10 will stop these instruments working, but the reverse lights won't work as well, and that hasn't been mentioned.
Don't rely on a fuse "looking good". Soft blown fuses aren't always obvious.
All E30 fuses, except one, are in the fusebox, plus cars with a rear battery have a fusible link in the smaller lead, close to the battery.
I've never known a fault with a lithium board that stops them resetting. The most common fault is that the rev counter jumps up off of its stop when the engine is stopped.

Post Mon Mar 19, 2012 10:22 am

I doubt that my problem is a fuse. Everything works except the resetting of he service lights.

My rev counter does have the "twitch" though...

I cant see that changing the batteries would help either, given tht mine give the full 3V.

I'm stumped.

Post Mon Mar 19, 2012 11:02 am

OK, forget all that.

Woeful schoolboy error was to blame....

Post Mon Mar 19, 2012 1:51 pm

clipper wrote:OK, forget all that.

Woeful schoolboy error was to blame....

Do tell! We promise we won't laugh.

Post Mon Mar 19, 2012 5:28 pm

I was connecting pin 6 to earth instead of pin 7....
Lucky that 6 does nothing important!

Post Tue Mar 20, 2012 7:49 am

changed the fuse and still the same...all the l e ds on service indicator working just the rev counter and mpg not working...
reverse lights working ok..

Post Tue Mar 20, 2012 4:42 pm

Me too - tech1 325i sport ...

Lithium batteries in SI test 3 volts. LEDs work.

Not working:
Rev counter and MPG (rev counter used to twitch when ignition switched off)
Interior lights
Boot lights
Glove box lights
OBC
Permanent 12V to radio (switched 12V acc. works and shows battery voltage, ground tests good too)

...they all failed at the same time.

Fuse 21 shows 12V at the fuse box and fuse is OK

Post Tue Mar 20, 2012 7:36 pm

Thanks for all the help lads...the car had been parked up some time and the battery was knackered so I fitted a new car battery and bingo!!!rev counter and mpg now working...thanks again!!!