2002 C-Class with random major electrical problem

I have a 2002 C-Class. Approximately twice per month but at very random intervals, it suffers a total electrical shutdown. I am driving along, and suddenly speedo/revs/fuel drop to zero, wipers stop, indicators and lights
stop functioning, radio goes silent - but engine carries on operating. I have not yet dared to try out the ABS etc in this situtation. After about 5-10 seconds, everything normally comes back to life, though this morning (while on the motorway) I had to pull over onto hard shoulder and restart the car to get everything working again.
I have rung the MB dealer and they claim that they will have to see the car to diagnose the problem. But from previous experience with them, I know that they will just rip out all the electronics, replace everything, and then give me a huge bill. If it does not solve the problem, I will not be able to prove anything because the problem is not repeatable, and occurs only at random intervals.
Has anybody ever heard of a problem like this?
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Not heard of such an instance but logic suggests a loose ground (earth) connection, not between the motor and the battery but between the chassis and the battery or the dash / instruments / ignition switch and the chassis.
Suggest the inquiry start at the battery and work outward from there.
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It is more complicated than that. FOr example, the radio goes off - but if I press the "on" button, it restarts - ie it has battery power. This seems to be more a computer bug somewhere in the car.
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Ric wrote:

I'm not an expert on the W203's, but my guess would be:
1) Replace battery.
2) Replace Over Voltage protection relay.
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IMHO, your car's radio shuts off due to a momentary power interruption.
I retain my theory of a loose ground connection.
My E320's battery is located under the rear seat. It has the conventional battery posts but attached to the post clamps are various cables - beyond the ones molded onto the post clamps. Your car may also have this Christmas Tree arrangement but one cable may be loose.
Simple enough to check, if only to know it ain't THAT!
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I have a 2000 CLK 430 and about everything in the car has a computer and they talk to each other all the time over a common bus. The engine is on a seperate bus. CAN C and CAN B bus. One thing bad on the bus could mess them all up. Jerry in Ohio
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I think you are more on the right track there.
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