1997 S500 - Oil Pressure Gauge Drops to zero.

[bolomiester]

I bought this '97 S500 a week ago. When I first drove it I looked at all the gauges while it was idling and everything was good, including the oil pressure at about 2. I test drove it for about an hour and it ran, idled and shifted perfectly. It wasn't until I was half an hour into my trip home that looked down and saw that the oil pressure gauge was at zero. I pulled over immediately but when the car settled down to an idle speed the gauge jumped back up to just under 2. Thinking it was probably a defective sending unit, I started to accellerate and as I did the gauge started increasing until it hit the top and it dropped back to zero. At that point I was sure it was the sending unit so I replaced it with a Mercedes OEM unit. It did not fix the problem.

I have an all data account for this car and found this tech bulletin:



Apparently I need to replace the circuit board. Is this something I can pull out of a salvaged cluster. Does anyone know how to open the cluster up to get at the board?

Baring that, can I install a salvaged cluster without the car's computer system having a bad reaction, like posting a warning on the cluster or refusing to work correctly?

My mechanic tested the oil pressure with a separate gauge and it's fine. I've also taken the car on a 600 mile trip and it ran perfectly, but it sure is scary to look down at the oil pressure gauge and seeing it at zero, plus if something did go wrong I wouldn't know about it until it was too late.

Thanks!