Instrument cluster not functioning correctly!

You could bet that the problem is due to failing electrolytic capacitors in the instrument cluster! The E32 suffered from this in a big way, I guess that the E31 is getting to an age when they are starting to give up. I'll see if I can find a 'How To'......

After reading this post:

http://forums.bimmerforums.com…php?p=7814142&postcount=4

I wonder if the problem is with the General Module which does have capacitor issues as seen in an earlier post. A quick look at the circuit diagram does show a data line from the ZKE to the Instrument Cluster that serves Fuel, temperature and rev gauges.....so, most likely the capacitors in the ZKE then!

Yes-most the capacitors in the E31 were moved from the instrument cluster to the general module. The problem seems to take a bit longer to show up than it did in the E32 but it is there nonetheless.

I have seen a DIY but don't remember exactly where. Mind is slipping.

More information in this post:

http://forums.bimmerforums.com…/showthread.php?t=1140955

from revtor

When using my picture as a reference, double check the polarity of the capacitors before removing them from the board. My picture is correct, but at bimmerforums.com one member recalled his capacitors were all in the same direction so there may be different board revisions! More and replacement information is in the thread Timm linked to (general module success!).

Failing electrolytic capacitors in the A1 General Module (GM) are a common issue with older E31s due to the limited lifespan of these components, but your car is relatively young at only 12 years. There is of course no exact expiry date. The conditions in which the capacitors have to operate have great influence on the lifespan. Some fail after 10 years while others last over 25 years. Of course it never hurts to replace the capacitors.

But just like Timm I don't think your issue is caused by the GM. Failing capacitors in the GM usually cause weird or non-functional behavior of the power windows, wipers, interior lights,... Things controlled by the GM. The instrument cluster on the other hand is not controlled by the GM but the A25 EKM (Body Electronics Module).

If I recall correctly there is only a single electrolytic capacitor on the EKM board. I forgot to write down its specifications so if anyone opens his EKM module, please let me know its capacity, voltage rating and temperature range - thanks! Opening the EKM is a bit more difficult than say the GM because it has protective shielding which needs to be desoldered.

Another common issue at lower temperatures are failing solder joints. Low quality solder, improper heating of pad and lead, mechanical stress,... creates so-called cold solder joints or solder joints that are prone to microscopic cracking. This may cause really weird behavior at lower temperatures. Simply touching the bad joints with a soldering iron fixes this issue. Finding the bad solder joints is another issue, though...

Zitat von revtor;72348

Opening the EKM is a bit more difficult than say the GM because it has protective shielding which needs to be desoldered.

You either need a bloody hot iron or better still a torch
Alternatively lots of patience with a soldering iron nicely heating the whole shell. Once the patience has worn off a screwdriver cum brute force attempt will do

Pictures (clickable) of the EKM and the lone cap inside (also the 9C356 pendant to the one located in the instrument cluster):

Cheers
Reinhard

Thanks for the specifications of the elco, Reinhard!

I imagine a small 15 to 30 W soldering iron for electronics may not be able to provide sufficient heat to warm the large shielding plates, but a 100 to 200 W soldering gun should work just fine (I advise against using the gun to solder the elco(s) or reflow the joints, though). I had no problems removing the shields using a 80 W temperature-controlled soldering station. Of course a soldering station is a waste of money for those who don't use it frequently. But a standard 15 to 30 W soldering iron and a 100 to 200 W soldering gun don't cost much and can be found in most DIY supply stores. Everyone who occasionally wants to perform repairs to electrical or electronic systems should have those in his/her toolkit. If you need it only a few times a year, the cheapest will do. I've seen kits of a low power iron, high power gun and a few additional tools for as low as 20 EUR!

Would really concider using a 60 to 80 W temperature-controlled soldering station, as you need heat to transfer fast into the soldering and not heating up all other close by components.

A 30W soldering iron is usually to week for desoldering purposes and often ends up in damaging the PCB instead.
If you don't have some soldering skills then I would not recomend to do this yourself, get help.

Also see that these component are having feed trough solderings ( both sides ) this means that enough heat need to be transferred to the other side to get component loose. do not use any force.

I would have replaced these capasitors with 105degrees C ones as they are of a higher quality and last longer, if possible when working on electronic I always do.
They can also take high temperatures better without drying out.

Some more pictures of the EKM

Cheers

As you have already suspected the problem is with the Body Electronics Module (EKM). This lives under the LHS of the dash. Have a search through these Forums and you will find pictures of it and methods of repairing it.

EKM and cluster are always paired if used.
The a.m. 93C56 critter holds the data (VIN, mileage) The same lives in the instument cluster´s PCB.
I don´t know of anyone who has swapped that one out but someone has to be first - after all it does have 8 legs only
Cheers
Reinhard

HAVE A LOOK HERE.
http://forums.bimmerforums.com…/showthread.php?t=1425831

koenig dave: Ferret101's problem was one of the main fuses which took out half the electrical system of his E31. The instrument cluster failure was just one of the numerous items no longer working. Since there was no relation between several of the failures apart from the power, it was pretty safe to assume the problem was caused by a fuse. Sandwich on the other hand only experiences a "broken" instrument cluster. Since the instrument cluster test does work, there's nothing wrong with the cluster itself but it appears it doesn't get data to display. So the EKM module is a very likely suspect as sandwich already thought and Timm suggested.