Econometer / MPG gauge

Post Sat Apr 02, 2016 6:54 am

Used my E30 for the first time in a few months yesterday and noticed that the econometer isnt working properly.
It swings from 0 to max and back again with nothing in between regardless of throttle position.

I get the feeling that this will be SI board related ? But there are no other isses with the cluster - rev counter, speedo and both other gauges working as they should.
The only other thing i have done recently is grafted on a new plug to the speedo sensor - but as the speedo works properly i cant see it being that.
Off the top of my head i cant remember what the SI is showing at the moment - is it worth trying a reset just in case ?

If that doesnt work Is it a case of checking and fitting new SI batteries ? This is one E30 job ive never done

Post Sat Apr 02, 2016 8:15 am

Sounds like it's the SI batteries Rob, mine is the same mate.

I've tried soldering new batteries, it does work but it's tricky and you have to be dead careful.

Post Sat Apr 02, 2016 8:23 am

Cheers jim my soldering skills arent great but at least its something that can be done on a bench i guess

Post Sat Apr 02, 2016 4:59 pm

No harm in trying really. The hardest bit is melting the solder to disconnect the old batteries, last time it also melted the pin solder and the connectors came out, so needed re-soldering.

Well worth giving it a go for the price of a couple of batteries.

Post Sat Apr 02, 2016 5:14 pm

jimbom30cab wrote:No harm in trying really. The hardest bit is melting the solder to disconnect the old batteries, last time it also melted the pin solder and the connectors came out, so needed re-soldering.
Well worth giving it a go for the price of a couple of batteries.

Connectors are welded to the batteries. You're supposed to unsolder the pins to remove them.
New batteries come with tags attached, but are unlikely to be the same as you removed, so a couple of wire links are normally required.
I doubt if new batteries will solve your problem, but it's not impossible, so I suggest, as with any fault, you TEST before ordering new.
Remove the board from the cluster, place it in your freezer for fifteen minutes, and then measure the voltage across each battery.
Don't forget that there are two completely different types of battery used on these, which are not interchangeable.

Post Sat Apr 02, 2016 5:17 pm

If you doubt that the SI board is the problem Brian am i just looking at a complete new set of clocks ? In which case can the speedo be swapped over to retain the correct mileage ?

Post Sun Apr 03, 2016 3:52 pm

The speedo. is very easy to swap between clusters - it just unplugs after removing the four small screws on the back of the case, BUT the fault you describe may be partly due to a fault on the speedo. circuit board.
The circuit board can be swapped over, although I've never done it, but it's not difficult to set the odometer to any figure you desire. Requires a bit of force on the mechanism, but I've never broken one yet.
Check the batteries first (and the ones on any replacement cluster you fit.)