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Old 10-04-2000, 08:13 AM
Posts: n/a
Originally posted by RobJ16v:
The 4matic indicator light is staying on
in my 1991 300TE 4m. I have already replaced
the stop light switch,and it still stays on. Does anyone else have an idea of what to check next?

My problem is now solved, here's what happened:
1. When the 4M light(the one on the lower right of dash, not center off speedo)first came on, I converted the car to 2-wheel drive mode (as suggested in the owners manual, and by one reply to the posting)using the "test" lever (de-activates hydraulics).
2. After replacing the stop light switch (which is the most likely failure mode)to no avail, I gave in and brought the car to the dealer.
3. Interestingly the dealer informed me that when an owner releases the 4M with the "test" lever, it will clear the error code in the 4M computer memory. So they don't advise using the "test" lever unless the 4M ACTIVE light stays on in the center of the speedo ( which is really what the owners manual says too.)
4. After reactivating 4Matic and driving to produce a new error/fault, the dealer checked the computer. The computer told them the problem was a bad STOP LIGHT SWITCH.
5. I informed them that I had just replaced the stop light switch with a genuine Mercedes part; we verified again that the 4matic uses the same stoplight switch as a regular 300E.
6. A little stumped, the mechanic contacted MB Engineering. Mercedes told him to bleed the 4M hydraulic system. Thankfully, this cleared the fault condition.
Problem solved.

Thanks to all who replied!
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