Some help please - 87 300TDT consol lighting issue - PeachParts Mercedes-Benz Forum

old goat · #1 10-26-2009, 10:25 AM

I am doing some repairs on my son’s 87 300TDT and have come up against one issue I just cannot seem to solve. Not one of the center consol lights work including the window button area. All the various switches work but no lights. I have the instrument cluster pulled and everything out of the consol and cannot find a wire issue so far. The lights in the cluster work and the dimmer switch is working fine. I borrowed an illumination control unit from a friend but that is not the issue either. Anyone have suggestions? Has anyone experienced a similar problem in the past?

Thanks

Jeremy5848 · #2 10-26-2009, 03:11 PM

Your car has an electronic relay behind the instrument cluster that controls all those lamps. The cluster lamps are controlled directly by the rheostat in the cluster but all the other lamps go through this "amplifier" so the total current load doesn't burn out the rheostat.

The "instrument illumination control unit" is N40 in Mercedes schematics and the part number is 004 545 08 32. It is pricey, a junkyard unit would be a good alternative. You have to pull the cluster and then undo two screws to remove a bracket holding N40 and N2/4 (the "warning module"). N40 is the one on the right.

It is also possible that Fuse 9 is blown; it provides power to N40. Interestingly, my '87 has a bad wire to N40 and it gets no power; I rewired it to the clock circuit on the same fuse.

BTW, your car is a "TD," not a "TDT."

Jeremy

old goat · #3 10-26-2009, 04:46 PM

Thanks Jeremy

I actually have tried the borrowed illumination control unit but only to the plug without mounting it. So I will pull the original unit and take a look at the rear connections. I appreciate the answer. I also need to make sure the power is being transferred although I know the plug has power to it via a meter test.

I know it is referred to as a TD and also have seen TDT. My tendency to call it a TDT is the fact that my son bought it from the original owner in Arkansas and that title had TDT on it. May have just been a local error. Whatever, we both know what I am talking about in the description.

Frank

old goat · #4 10-29-2009, 08:38 AM

The answer is the little red cluster fuse. Although it registered voltage passing through it, the fuse was so near to being shot that it could not carry enough amps to light a 2 watt bulb. So now I will have to find one. Anyone know the amp rating for that fuse or where to buy one?

Thanks, Frank

babymog · #5 10-29-2009, 10:41 AM

I have some over in Holland, how far away is Chelsea?

old goat · #6 10-29-2009, 11:05 AM

Chelsea is about 15 miles west of Ann Arbor so quite a way from Holland. I would be glad to reimburse you for the fuse plus shipping if that would work.

okyoureabeast · #7 10-29-2009, 11:05 AM

Don't worry about the rogue T. It's a running gag on the forum.

For the record on my insurance card I drive a 1985 Mercedes Benz 300DT :p

Jeremy5848 · #8 10-29-2009, 11:12 AM

Interesting. That fuse appears on later 124s -- my '87 didn't come with one but when I was doing an upgrade I switched to a later cluster and the fuse came along. I always wondered what it was for. BTW, I also have spares but Jeff is a lot closer.

Jeremy

babymog · #9 10-29-2009, 10:17 PM

Quote:

Originally Posted by old goat

Chelsea is about 15 miles west of Ann Arbor so quite a way from Holland. I would be glad to reimburse you for the fuse plus shipping if that would work.

PM or email me your address, I'll happily give you one via USPS.

old goat · #10 10-30-2009, 06:12 AM

I just sent an e-mail via your contact info on this site.

Thanks, Frank