No light! - PeachParts Mercedes-Benz Forum

dieseldude · #1 02-26-2003, 10:41 AM

Well, first project on my W115 will be tracking down the lack of dash lights. Even though without seeing the speedo, I don't run the risk of speeding, I figure lack of dash lights is still a bad thing

Popped out the cluster, replaced some burned out bulbs, and made sure everything was plugged back in nice and tight. Then, I cleaned up the fuse block and put all new fuses in - still no lights.

It is just the instrument cluster, light switch, AC indicator and HVAC controls that are out. Radio and all other interior lights work. Any ideas fellas? Is there another connection under the dash somewhere that's come undone?

Regards,
- Ryan

Fisherman · #2 02-26-2003, 11:28 AM

i thinkt hat the rheostat often goes bad in these, especially after sitting for a long time.
You might try turning it back and forth a bunch of times to see if it helps at all.

The other thing is that some guys I think have actually hardwired the connection to full bright bypassing teh adjustment in the relay by soldering a wire across the rheostat.

dieseldude · #3 02-26-2003, 11:50 AM

Hey Fisherman - is the rheostat the dimmer-knob controlled by the knob opposite the trip-odometer-reset knob? My first thought was the dimmer was just turned down to low, and noticed the mechanism behind it was very corroded when the cluster was out.

I sprayed some contact cleaner in it and moved it around a few dozen times to clean it, but with no results. Guess a new one is in order if were talking about the same thing...

Regards,
- Ryan

Fisherman · #4 02-26-2003, 11:53 AM

yeppers, that's the one.
I know mine has some fade spots int eh adjustment when you try to set minimal lighting at night.
I just cranked it back and forth a bunch of times and it got better. Not fixed but better.

Stevo · #5 02-26-2003, 11:58 AM

I soldered a little "jumper" across the back of the rheostat like Fisherman said and it works great, just the right brightness for my eyes

The Warden · #6 02-26-2003, 12:40 PM

If I remember right, new rheostats are real cheap (like less than $10 from some sources, although I just checked Fastlane and it's closer to $30)..I could be wrong, though...

How bright would you all call the dash lights in perfect working order? Were I to guess, I would guess that mine are pretty dim, although the rheostat seems to be working normally...

Also, how many bulbs light up the instrument panel? I was under the impression that 2 bulbs did the job, but was looking around on ************************ and they say that 6 are required for the instrument cluster...

dieseldude · #7 02-26-2003, 12:57 PM

Warden - thanks for the rheostat info. I can however, atest that 6 are need for every light in there (including turn signal, brights, battery, parking brake, etc.). As far at the main gauges like speedo, fuel, and oil there are only three that I remember (with fiber-optic wires lighting to the HVAC controls from the speedo bulb.)

My W123's lights are dim, but this is a known issue. Can't speak for the W115's since mine have never been lit and I can't remember what my previous W115's looked like...

Regards,
- Ryan

The Warden · #8 02-26-2003, 01:15 PM

Quote:

Originally posted by dieseldude
I can however, atest that 6 are need for every light in there (including turn signal, brights, battery, parking brake, etc.). As far at the main gauges like speedo, fuel, and oil there are only three that I remember (with fiber-optic wires lighting to the HVAC controls from the speedo bulb.)

Oh, DUH...I wasn't even thinking about the warning lights and the turn signal lights.

And, actually, on the 123, the ACC controls have their own lights...I don't think there's much in the way of fiber optics on them. I had two bulbs out in my ACC (there's 4 or 5 total; can't remember exactly), and replaced both, and the ACC controls light up much better now...

Actually, if you count the brake light, glow plug light, turn signal indicators, etc, on the 123, I count 8 lights, not counting whatever lights light up the instrument cluster itself...

diesel don · #9 02-26-2003, 01:45 PM

dieseldude:

couple of thoughts

1) the idea to solder a jumper is phenom. i've done it twice with great results

2) when you have the cluster out, paint the housing area (where the bulbs go) white as it dims to yellow over the years. this will produce a 30% brighter dash presentation. this has been noted several times on this forum.

3) i had to create a separate ground on my '83 before anything would work on the dash. as it was, something was keeping the metal edge from grounding on the car. took an extra wire and presto, everything worked.

dieseldon

dieseldude · #10 02-28-2003, 03:53 PM

Thanks dieseldon - I have heard of the repainting trick for W123's, just never got around to it. Replacing the bulbs was enough of a difference for me.

Back in W115 land - guess I won't need a new rheostat for a little while afterall. Spinning the knob around a few dozen more times, the lights sputtered, and jumped to life! Spinning the knob doesn't evenly dim/brighten, but the the full-on position works, so I'll leave it alone for now.

Still not getting any light to the HVAC controls/AC light, is there a separate feed/bulb for these somewhere? I seem to remember my first 240D having fiber-optic lines going to the controls, and I'm now wondering if I disturbed them with the cluster out(?)

Thanks again for any input!

Regards,
- Ryan

Fisherman · #11 02-28-2003, 04:21 PM

If this is on the 115 I'm not sure there are lights on these controls. If there are mine don't work either...

There is a plug on my center console located on the right hand (passenger) side that when removed appears to have a bulb in it but what it lights I have no idea. Maybe that's where my lights live adn this one is burned out. For the dash controls there may be backlighting of some kind but I have never looked for them.

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