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This is my first post here. We've owned (2) Benz's, a 2006 E320 CDI (loved that car), and we still have a 1981 240D.

As we all know, these cars are notorious for cluster light issues. After I got the car, I went thru it, and fixed all of the lights, and had them working great. Then we let the car sit for a while and didn't drive it. Now my youngest is wanting to drive it, so I got it going again.

The other day while she was driving it, the instrument panel lights quit, then the A/C, then pretty much everything electrical, and she couldn't get it started. When I got there, I immediately noticed that the positive battery terminal had melted! This was sort of a weak junk battery, so I figured it just dropped a cell or something, and overcharged.

Changed battery, and it seems to be charging fine.

But in the course of this whole thing, it blew the instrument panel fuse. No biggie I changed it. As soon as I turn on the lights, the fuse blows. Just for testing purposes, I changed to a bigger fuse, and the lights do NOT work, but it doesn't blow the fuse either. And occasionally, the lights would come on, but now they don't come on at all.

I thought that maybe I had a short in the dimmer rheostat. It was most likely bad, since it was all corroded, and looked like it had been hot, so I just soldered across the terminals, and the dash lights still don't work.

Interestingly, the light for the A/C switch works, and it's the only dash light that does.

I have looked at the headlight switch, but I don't know which wire to check on it to see if I have 12V at the instrument lights circuit. I have also wiggled the wires on the headlight switch, and none of them appear to be loose, and wiggling them doesn't make the lights come on either.

I have also looked at the wiring, and I can't see anything that's melted or messed up, but I'm not about to take the dash out to find out for sure, but the stuff that I can see doesn't look burned or melted.

Any ideas of where to look, or anything to try that will point me in the right direction???

CADman_ks
 

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i can't tell you where to look, but by using too large a fuse, you may have invited another mystery part deep in the guts of who knows what to melt. you may have to trace the whole instrument lights circuit back to the fuse box using a factory schematic to find where the circuit is broken.
 

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i can't tell you where to look, but by using too large a fuse, you may have invited another mystery part deep in the guts of who knows what to melt. you may have to trace the whole instrument lights circuit back to the fuse box using a factory schematic to find where the circuit is broken.
That's my plan today, is to trace it back. From the brief checking that I've done so far, I can't see anything that is melted anywhere, so I don't think that's the issue...

CADman_ks
 

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Hah! Your A/C light is the only one that works, and mine is the the only one that doesn't. Boy I wish I knew how to get to that thing.
I'd bet in that case, that just that one bulb is burned out.

You should be able to just CAREFULLY pry that switch out, working it from the top and bottom slowly.

Then, there will be a light socket on the back side of it. Just pull that out, and replace the tiny little bulb that will be in there.

PS: From your sig, it looks like your car and mine are the same color. That's a lovely color! I think that there's a reason that we don't have cream colored cars anymore!
 

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I'd bet in that case, that just that one bulb is burned out.

You should be able to just CAREFULLY pry that switch out, working it from the top and bottom slowly.

Then, there will be a light socket on the back side of it. Just pull that out, and replace the tiny little bulb that will be in there.

PS: From your sig, it looks like your car and mine are the same color. That's a lovely color! I think that there's a reason that we don't have cream colored cars anymore!
Yea, they're my favourite. Though apparently it's the Taxi color. Also, my A/C switch is the kind that you can pull when on and it engages the defrost, can you pull that one out?
 

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Hah! Your A/C light is the only one that works, and mine is the the only one that doesn't. Boy I wish I knew how to get to that thing.
MY BAD!!!

I told you wrong. That switch does NOT come out from the front.

The only way that I get to mine is to use the same procedure, prying on the top and the bottom of the panel that holds all of the switches. I'm actually able to pry off that faceplate.

Then, the A/C switch will stay in there. Then you just change the bulb...

CADman_ks
 

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'86 W123 200, OM617 non-turbo, bastard 5-speed; '95 W202 C250 Diesel, OM605 non-turbo, 5-spd man
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I remember when my instrument panel wiring melted. Search the W123 forum for "nervous breakdown", it will show you.

I'm too tired to link you now...
 

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Hallelujah!!! I got it fixed!!

As it turned out, I traced all of the wires down, and I DID have power at the headlight switch, and I had power at the plug going into the IP. I finally decided that something had to be amuck in the IP.

I took it apart, and sure enough one of the runs to the rheostat was melted in two. I think what happened was when the battery went south, it weakened that joint, but didn't break it. After several fuses, and a weak link there, it finally broke, and then they woudln't work at all.

I soldered across the gap, and looks like it's holding. If this happens again, at least I know how to fix it, albeit a PITA!

For the record, I have gone back to an 8A fuse in that circuit like it's supposed to have and all lights are staying on!!

Thanks for all the help and replies!!!

CADman_ks
 
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