1987 300TD Turbo - Instrument lighting not working
 

On my 1987 300TD none of the instrument lighting seems to be working.

None of the instrument lights or center console lights seem to be working.

The fuses are not blown.

Is this the kind of issue where one light may have failed and taken down all of them?

Where should I start looking to fix this?

I also have a 1990 300TE that has its lighting working fine so I can pull parts from that for testing if needed or comparison.

Check first the rheostat (dimmer) in the instrument cluster.

Jeremy

This is the usual cause. Just turn the dimmer knob back and forth about a hundred times. At first you may see an occasional glimmer of light, but if you are luck, eventually the lights will stay on.

If that doesn't work, make sure you are checking the correct fuse and make sure it is a new brass one or one on which the fuse ends and sockets have been cleaned.

Many owners jumper across the dimmer (easy to do if you take cluster out)

But on my car, the cause of lack of lights was a burned trace on the cluster circuit board. Instead of the fuse blowing, the cluster traces blew. I had the proper 8amp fuse, but for some reason the traces were the weak link. I posted elsewhere on this forum about how I hard wired the cluster, eliminating the cluster traces.
https://dl.dropboxusercontent.com/u/...r%20traces.jpg

Are any other lights on? That should help narrow your search. If your PBU, vent flap nobs, or shifter surround have lights lit your cluster(most likely the rheostat) is suspect. No lights anywhere means a fuse or something other.

Have a look at this thread. I posted on this one and I suspect you might have the same problems.

http://www.peachparts.com/shopforum/diesel-discussion/319513-w124-electrical-fun-two-problems.html

None of the lights work - none of the center console or instruments. I had to wait till it got dark enough to see the interior lights. I will try working the rehyostat more.

If the rehyostat goes can it take all the lighting with it?

I will tear into this tonight and tomorrow.

Yes, a bad rheostat can take out all your instrument lighting.

Definitely go to w124-zone.com (you will need to register but it's free) and get a copy of the wiring diagram first. Also the FSM linked there has all the work instructions for how to remove the instrument cluster and center console, you'll need those to know how to access the circuits for testing.

Pardon my lies, a rheostat will take out all the things i listed i forgot that they all dim via the cluster. I know you said the fuse wasnt blown but is it old? I went to the trouble of soldering mine to later learn that my fuse although not blown was corroded just enough to not work.

It was the rheostat. I bypassed it for now with a wire I wrapped around the posts, but I will try and rebuild it. If that does not work I will replace it eventually.

I did break my center vent pulling the instrument cluster out. I removed the left vent and than decided to remove the right to make the job easier and broke it with my overzealousness.....

So if anyone has a center vent for sale let me know.......

Oh yes and seriously thank you guys. All of this help is very appreciated.

Ill check the yard for a vent. I explosively disassembled two before learning how to put all the pieces back. They can be resembled if the pieces haven't truly snapped/broken. I counted once the center vent has something like 30+ individual pieces that can be disassembled and reassembled.