Hello all MB lovers,

This morning my 94 C220 just won't start, the battery, starter are all OK. No matter how I crank the starter there is no any sign of engine combustion. I think the problem should come from electrical firing system and the first one on my mind is the famous OVP relay. Story back to March this year when I had my engine wiring harness replaced, the dealer recommend me to replace the OVP but I did not. Because My OVP's date code is 050996, part # is 000 540 67 45. I thought this is an updated one.(I bought my car last year). This morning's problem proves I was wrong at that time.

OK, continue. First I use a multi-meter to measure pin #1, it got 12V, good! Pin #2, no voltage appears. From the diagram on the side of OVP, Pin #2 in activated by K3 replay. TO be safe I consult my mechanic uncle he said he used to have this problem on a E220 which failed at Pin #2. I can temporarily jump pin #1 and Pin #2 to provide pin #2 voltage. I did and it started, wonderful! Then I drove to a nearby mechanic to order a new one. The new OVP is exactly the same as the failed one, part # is same and also made in Hungary, except date code is 011000. I think it's made in year 2000.

I am happy to share my story with you in case someone on this forum has this problem and can not get help in time.
I've learned so much from here and love this site so much.

Charles
94 C220 with 48K miles

very productive info....thank you.