Instrument cluster question

[MikeyL]

My 93 500E has some kind of short in the cluster, apparently on the left hand side with temp/oil pressure/fuel. I am not a DIY person, but my mechanic tells me that there is a circuit board that is bad that is causing the problems. Apparently the grounding of that circuit board isn't working on it either.

It got sent to Palo Alto Speedometer, and they tried to repair but it didn't work. He said my daughter's 91 300E has a different more mechanical type of setup...

Does anyone know anything about this, and if so how I can fix that problem? At first the fuel gauge was bouncing around, and now that seems to be okay but the outside temp gauge goes on and off sporadically and I think other lights might be affected. Thanks for any help.

 

[emerydc8]

The outside temperature gauge doesn't go through the circuit board. It just screws into the cluster from behind and there's a plug that goes into the back of it. I recently had the turn signal clacker go out and it turns out that the circuit card on the left cluster (fuel/temp/oil pressure} controls that. I bought a cluster on e-bay that was from an E320. Even though the rest of the cluster didn't work on my E420 (tach/speedometer), I was able to swap out the left cluster and it's been working fine. It doesn't take a lot of mechanical skill to do this repair. There are tools (hooks) you can buy to hook onto the back of the cluster and pull it from the dash. That makes the job a lot easier. But if it's just your outside temperature gauge hanging up, I don't think you need to worry about the circuit card.

 

[gsxr]

If the fuel/oil/temp gauge pod is bad, you can replace it with a good used one from a 1993-95 6-cyl sedan, and re-calibrate the fuel gauge via the pot soldered to the board. @Jlaa posted detailed instructions on how to do this so it will work in a 500E. The oil pressure and engine temp gauges are identical across all 124's, only the fuel gauge portion is different between models.

The 1991 300E gauge should be nearly identical, as I think the "economy" vacuum gauge was deleted as of 1991? It's not "more mechanical" than later gauges; however the SPEEDOMETER is fully mechanical on all 124's without V8 engines, while the V8 speedometers are electronic instead of mechanical.

 

[emerydc8]

Thanks, Dave. I was hoping you'd jump in and add some pertinent details.

 

[MikeyL]

Thank you both!