I can't seem to get my instrument panel lights to work. Can't see how fast I'm going at night. One of the things on my list of things to fix.

I pulled my instrument cluster and noticed that the spring in the ?dimmer? was stretched out. I figure this spring is part of a rheostat/variable resistor but also realize that there is no easy way to fix that I can see.

I get another instrument cluster that has an un-stretched spring. The spring is loose and almost bent while I was testing it. I did alot of work on the cluster. Clock still doesn't work, painted the needles with florescent paint, clean it, checked all the bulbs. Had to superglue the spring into the rheostat to keep it from bending. Still no lights in the instrument cluster. Retained my original speedo too.

All my other indicator lights (flasher, charge, brake, high beam, seat belt and glow plug) work and gauges (fuel, temp, oel, speedo, odo + reset, tach) work fine too - some improvement.

One thing though... the lights in the rest of the dash don't work either... environment controls and such. Fuse?

Codifex
1981 240D SkyBlue (waiting on an engine)
1983 300DTurbo w/sunroof

Solder a jumper wire around the rheostat.

The instrument lights will magically reappear.

Possibly. Check all fuses.

That reminds me, I put my fog lights on the other night and they went out after about ten seconds. I need to do some fuse checking myself.

__________________
Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

That's one possibility - also check all the fuses just to be sure. If that doesn't work you'll need to dive deeper. On mine, the circuit board copper foil lines were actually burned out - something fried them unexpectedly.

To find that, I had to disassemble the gauges individually by removing the retaining screws from the back of the instrument panel working from left to right until I got behind the gauge that contained the oil pressure, temp and fuel. It's not hard, just go slow and keep track of the screws.

Right under one of the gauges, I noticed that two of the copper foils were damaged (burned out) with some visible discoloration around it. The resulting open circuit was my problem. To fix that, I carefully soldered small 'jumper' wires to bridge the missing copper lines and voila - the light were back on.

So if both instrument cluster AND climate control lights are out you may need to look for a damage in the circuit board. When you see it - you'll know it.

__________________
1987 Mercedes 300SDL; SOLD
1985 Mercedes 300D; SOLD
2006 Honda Pilot - wife's ride; 122K;
1995 Toyota Land Cruiser - 3X locked; 182K

Brian,

I will see what I can do about the jumper wire. I don't really change the intensity of my instrument lights that much anyway. Would this rheostat also control the environment lights as well?

Which traces do I solder the jumper to on the circuit board? Do we have a snapshot?

Skippy and MercFan,

I'll check those fuses too. I'll get back with the solution when I have it.

Codifex
1981 240D SkyBlue (waiting on an engine)
1983 300DTurbo w/sunroof

Search is your friend:

http://www.peachparts.com/shopforum/showthread.php?t=259970

The console lights (climate control, radio, etc) feed off the rheostat, so that circuit path is likely your problem. But if your clock also isn't working you may have an additional problem. Or maybe just a busted clock.

Use contact cleaner when re-assembling. I also recommend Stabilant, but you might find that a bit pricey.

My car is a high milage 300SDL that was brutally neglected by the PO, I got it with no dash lights as well, I went through everything, new fuses (they can lookperfectly servicable and be bad), chasing wires, replacing all bulbs and so on.

After all that I read a post similiar to the one above outlining the circuit board etching popping like a fuse. I found mine had done that adjacent to the rheastat so I soldered it back togther and jumpered the rheastat (which tested good on ohm meter) I just didnt want to deal with its failure down the road. I have lights now and its reeeeally nice.

I also noted that they are actually bright enough with the factory bulbs so I didnt need to do the LED conversion.

__________________
87 300SDL (Silver/red)
08 VW GTI (Sold)
89 F250 5sp turbo diesel
00 Triumph Sprint ST (4sale)
00 Polaris Xplorer 400 4x4
09 Kawi KLR

On the back of the rheostat, the two pins circled, solder a wire there.

Attached Thumbnails

 

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83 SD

84 CD

I soldered my jumper wire directly to the circuit board, I stripped one end about 1/8" and soldered it directly to the rheastat pin on the etching side of the board.

The other end I stripped about 1/2" and used the extra length of bare wire to cross the other rheastat pin (the one adjacent to the damaged area) and extend to cover the damaged etching to give it something more than just solder to hold it together.

If your circuit board is NOT damaged in this way than IMHO you are far better off to solder your jumper wire across the back of the rheastat as pictured in the last post, this so the circuit board remains intact and unaltered. You can then replace the rheastat if you feel compelled and its just as new and not "fixed" as it is on my car.

__________________
87 300SDL (Silver/red)
08 VW GTI (Sold)
89 F250 5sp turbo diesel
00 Triumph Sprint ST (4sale)
00 Polaris Xplorer 400 4x4
09 Kawi KLR

Thanks Casey, Yak, TooMany, Merc and Brian.

I'll pull the IC back out on my next day off and do the solder job on the rheostat. I have high expectation of a fix thanks to your collective advise.

The snapshot was very helpful. I'll post feedback soon.

Codifex
1981 240D SkyBlue
1983 300DTurbo w/sunroof

Got my,s to by turning it off and on about 50 times or so.They work now but are very dim,guess i got lucky.

__________________
How can we set back and say that the,CEOs of these big Co,make MILLIONS and MILLIONS is ok,and the working man gets the shaft. And Yes Iam far right wing.

Feedback.
Took me a while to pull the IC again but...

After soldering the jumper to the back of the rheostat and replacing a few bulbs, we have LIGHT! The console, CC and radio are all lit up nicely.

Thanks again for the help guys!

Codifex
1981 240D ChinaBlue (found an engine - hope it's good)
1983 300DTurbo w/sunroof