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Old 08-24-2002, 01:46 AM
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Angry What and Where's th $#@%^ OVP?

Can anyone tell me what the OVP does and where it's located on a '94 C280?

I've replaced plugs, wires, boots and end caps and the #@*%! thing is still running rough and smelling "GASSY."

This thing's driving me mad! (Well, I'm mad and not driving it.)

Thanks for your help!
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Old 08-24-2002, 07:21 AM
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Join Date: Jun 2002
Location: Cumming Ga.
Posts: 238
The OVP (overvoltage protection relay) is just what its name says.Its purpose is to protect the engine control unit from excessive voltage.Its unlikley that this is your problem though.Its very possible you have a air mass sensor going bad or possibly a ignition coil going bad.The 93 and some 94 year 104 engines had some problems with ignition coils made by "May Christy".
Mercedes Benz Master Tech
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Old 08-24-2002, 11:49 AM
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Dear RPM:

Thanks for that advice. I will check the coil manufacturer and the air mass sensor and let you know.

Have any ideas why the "Check Engine" light has never come on? Considering how rough the car is running, the lack of this light really surprizes me.

Thanks again!

Bob Crothers
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Old 08-24-2002, 12:01 PM
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Checked the coils. They are BOSCH - no May Christy. Guess I'll try air mass sensor now.

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Old 08-24-2002, 12:09 PM
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,768
OVP diagnosis also usually shows an ABS lamp on.

For your reference [ and cuz the OVP is another troublesome part on your model that has been up-graded], it is located behind the plastic pop- off panel behind the battery-- tall , aluminum can /fuse on top- one screw on the side for removal..

Check the part #
Old # 000 540-67-45
New- 000 540-52-45

Worth changing due to fail rate and low cost..

Other possible is the original wire harness should be checked for poor insulation- another up-grade...

Both of these are not "will they fail", but "when"
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Old 08-24-2002, 01:33 PM
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This is good information. Now that you mention it, although the ABS lamp does not stay on, I have noticed that it takes an inordinate length of time - after starting - for it to go off. It will sometimes stay on for two or three miles before blinking off!

I'll replace it today. Also, is the mass air sensor a difficult part to replace and, can you tell me where it's located? RPM55 suggested that it might also be the culprit.

Thanks for the reply. I really appreciate both you guys. I'm scared to death to take the car back to my local MB dealer. The last time I took it in, they said I needed a new window motor and regualtor and a new transmission and motor for the uniwiper.

The "Burned out window motor and regulator" turned out to be an unplugged motor and a missing rivet to the motor frame. Total cost to repair: $13 (had to buy a larger pop rivet gun.)

Thanks to a doctor in Oregon (who had performed "surgery" on his 280) I was able to remove the housing on the wiper. Inspection of the wiper transmission revealed that it was fine. The motor was bad and was replaced for about $110.

My Total cost: Less than $125 (The dealership quoted $1950)

I guess that's the price you pay when you only have one dealer in a city of more than 1.3 million people. Monopoly in action.

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Old 08-24-2002, 01:44 PM
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,768
On the ABS lamp info, The OVP is worth looking at..

If you find the OVP to be the old #, I would change it..

And go from there
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