Clusters - Motometer & VDO

[Mr_P]

Hi all

Long time lurker, first time poster :)

I have recently picked up my E30 320i Cab and since I have owned it, the temp gauge has never worked.

I planned on fixing it eventually, but then I had an overheating problem, and spending 2 weekends replacing the head, I am reluctant to drive it again until its working.

So I have tested the sender and the wiring which are both fine, I have resoldered the connection point on the board and I can tell the gauge is getting power as it moves slightly when the key is on.

I picked up a second hand cluster (a VDO), and this doesnt work at all in my car - it lights up, but none of the gauges work.

I pulled them apart with the view of swapping the SI Boards and found that has an 18 pin SI Board whereas the Moto Meter has a 15 pin board

Everything I have read tells me the clusters are interchangeable, yet its not working

Is there something I am missing here? its driving me nuts!!

[jlevie]

The clusters are interchangeable, but in this case both could have bad SI boards. In which case the temperature gauge would not work when either cluster is installed.

[agent]

Have you tried smacking the dash above the gauge? I have to do that every time I get in my car for it to work (yes I realize this is not a good long-term solution).

[dnguyen1963]

You have to check for the condition of the batteries. Good board/bad batteries or bad board/good batteries can cause this problem.

[Gregs///M]

I would not recommend you "smack" the dash like the above poster recommends. This can clean to premature solder joint failure and can make the problem worse or cause other cluster related problems.

I would first recommend to swap the SI board batteries with fresh ones. Other causes can be the Engine to Chassis ground cable, ground nuts behind each gauge on the cluster. 7mm nuts behind each gauge loosen up causing intermittent operation. Also check cluster ground lugs above the brake pedal. Remove the 10mm nut and clean all connections.

Most likely batteries since they are 20+ years old. Give me a holler if you need battery replacement. I have one pair left and it will sell quick.

[Mr_P]

Thanks for the replies

- Yes, I tried the 'dash smack' to no avail, I had tightend the nut on the back as well with no change - however I know the gauge it self is getting power

With the 'new' VDO cluster, both SI batteries are putting out ~0.97v (of 1.25 according to the batteries in there), however nothing on this cluster works in the car, other than warning lights and backlights (I have a 6cyl coding plug in there)

With the original Motometer cluster, the temp gauge does not work at all, and the fuel gauge jumps around occasionally, but other than that, everything else on it works.

I am going to give all the contacts on the VDO a good clean up and try that one again, but I really hope I didnt just blow $100 on something that won't fix the problem, given how much I have just spent on the engine.

[dnguyen1963]

The next step is to check for cracks on the board with a magnify glass.

[Mr_P]

Well, after pulling the VDO apart and cleaning the SI board contacts and re soldering a couple of dry joints on my desk over my lunch break (I work from home :) ), it is now working (I hope anyway - tested it and the temp gauge worked and went to full hot when I grounded the sensor), the fuel gauge, and rev counter work and the speedo moved when I drove down the driveway a little.

Hopefully all good from here!

[agent]

I would not recommend you "smack" the dash like the above poster recommends.

Well... to be clear, it was not a recommendation. It was a question which would help identify if the gauge was indeed getting power/a signal based on my experience.

Glad to hear you had some success OP.

[Gregs///M]

FYI, lithium SI batteries should be a minimum of 3V DC each. However this is not a true test to see if the batteries are good.

Each battery must be first removed from the circuit and tested with an ampmeter. Each battery should have a minimum of 400mA's of current when load tested.

A battery can have 3 volts but 300 mA's and I'd consider that bad.

[TobyB]

Each battery should have a minimum of 400mA's of current when load tested.

Into what sort of a load?

t