This question has our technicians stumped.........

The gent will pay for the answer.

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The vehicle currently has the following problems:

1. The front overhead light would stay on even when the key is out and all
the doors are closed; it could be turned off only with the overhead control
switch.
2. The master key would not engage the central locking/unlocking system.
3. The door lights, rear overhead and reading lights, as well as the trunk
light, would not go on.
4. When the engine is running, the overhead seat belt warning light keeps
blinking.

These are all resulted from replacement of the #15 fuse (8A). Last week the
power antenna started not extending its mast, and the front overhead light
would blink every time I turned on the radio.

This afternoon, I check the fuse box and noticed the #15 fuse was burned
out. So I replaced the 8A fuse and operated the radio a few times to observe
the power antenna to extend and retrieve its mast.

After a few times the power antenna start the same problem and the #15 fuse
would go out again. So I unplugged the power antenna unit connector and
replaced the #15 fuse.

But the #15 fuse would burn out the moment it was in the slot. I then
noticed that the front overhead light would not go off on its own when all
the doors are closed, unless I turn the switch off.

I then disconnected the (-) battery terminal for more than 20 minutes.

When I connected the battery terminal back again, with the #15 fuse out and
the power antenna connector disconnected, the vehicle seems to run just
fine, except the 4 noticeable problems described at the beginning.

Please advise."

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If you want to answer online, that 's great. The question is at:
http://www.all-parts.com/diagnostics...hread&id=80820
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He's offering $7.50.

THanks

It's been a while since I did wiring on Mercedes so if memory fails
you know the drill.

Somethings gone short or to ground in the #15 fuse circuit. Get the
wiring diag out and find everything that feeds off of that fuse.
Would be nice if you could pick out all the splice connection
locations and disconnect each one to isolate the the fault.

Personally, I would pull out all the door.trunk/hood switches first,
keep the wires from grounding, replace #15 and test from there. If
any wiring or rewiring was done - like aftermarket stuff- that would
be the second thing to disconnect. The third thing is ground. You
may have lost the ground on a subcircuit and this is backfeeding - or
not. The fouth place to take a hard look is all the wire bundles from
the hole in the firewall to every tie down attachment point for
looseness and abrasion.

You might also try using a breaker instead of a fuse. Loosen up the
fuse block and on the back, pick out any wires (there may be two or
more) that #15 fuse feeds. With the breaker in place, touch all feed
wires to find the hot one. If nothing else this will help to isolate
a subcircuit and a wiring diag should tell where the wire goes.

Not to insult anyone, but your customer has a glorified Studebaker
that was built by machinists. All the parts that could be machined
are a work of art. All the parts that could not be machined are an
afterthought. The wiring was designed by a retarded machinist who
got the job of electrical engineer and who has no concept of basic
wiring safety. Mercedes pulls full unfused battery power into the
car on a #10 wire and then feeds everything off that wire.

Sounds like this car is about due for a wiring harness fire, like so
many before it. Don't let your customer drive around with this
problem uncorrected. It may cost him the car.

This is a repairable problem, but it will cost more than 7.50$.

Pete

Mercedes - my daughter owns one, worked on many, less than impressed.