switch for dash lights

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

dougcullen@gmail.com - 30 Jul 2006 03:58 GMT

hello, i have a 1982 300SD...all the dash lights are out and i've been
told i need a new electrical switch under the steering column...where
can i find that part? Do i have to get it from the MB dealer or can i
use a generic part? How much should it cost?
Thanks,
Doug

Reply to this Message

Tiger - 30 Jul 2006 04:39 GMT

That's rheostat... dealer item only... boy, it is expensive. Try ebay. I may
have a spare... I'll let you know if I have one.

Reply to this Message

phollings - 31 Jul 2006 21:15 GMT

> hello, i have a 1982 300SD...all the dash lights are out and i've been
> told i need a new electrical switch under the steering column...where
> can i find that part? Do i have to get it from the MB dealer or can i
> use a generic part? How much should it cost?
> Thanks,
> Doug

I have a similar problem on my '77 300D: my instrument lights are very
dim. My rheostat (brightness control) works as I have verified because
the lights on the center console (HVAC) are bright and can be dimmed
correctly. Since this rheostat also controls the instrument lights, I
believe the connection is good that far, but something is causing the
instrument light branch of the circuit to be dim even when the rheostat
is turned to bright.

Please give me any suggestions on correcting this.

Thanks!

Reply to this Message

Tiger - 31 Jul 2006 23:49 GMT

I battled this with my older 380SE... changed all the bulbs... changed the
rheostat when it died... I hooked up the cluster direct to battery and the
light are super bright.

The only thing I can think of that cause this problem is the headlight
switch, but I never changed this so I don't know.

Reply to this Message

Richard Sexton - 01 Aug 2006 10:37 GMT

>> hello, i have a 1982 300SD...all the dash lights are out and i've been
>> told i need a new electrical switch under the steering column...where
[quoted text clipped - 10 lines]
>instrument light branch of the circuit to be dim even when the rheostat
>is turned to bright.

The relationship between voltage drop and luminous flux is far far from
linear. It's third order or something like that.

Bottom line is, crud on the rheostat plus old bulbs means dim dashes.

Replace or clean the rheostat, replace all the bulbs and clean the
plastic on the instrument cluster. I did this and it was like night
and day.

http://articles.mbz.org/instrument/renew/

Signature

Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
1970 280SE, 72 280SE | Home pages: http://rs79.vrx.net
633CSi 250SE/C 300SD | http://aquaria.net http://killi.net

Reply to this Message

Richard Sexton - 01 Aug 2006 10:34 GMT

>hello, i have a 1982 300SD...all the dash lights are out and i've been
>told i need a new electrical switch under the steering column...where
>can i find that part? Do i have to get it from the MB dealer or can i
>use a generic part? How much should it cost?

The dash dimmer rheostat is the culprit. I was able to *repair*
mine (naturally *after* I got a new one).

http://articles.mbz.org/instrument/dimmer/

Here's how to get it out:

http://articles.mbz.org/instrument/renew/

Signature

Reply to this Message

Tiger - 01 Aug 2006 14:59 GMT

Great article... I bought a new one when the other failed... but still same
thing... dim... sold the car already.

Reply to this Message

Richard Sexton - 01 Aug 2006 16:30 GMT

>Great article... I bought a new one when the other failed... but still same
>thing... dim... sold the car already.

The bulbs age. The filament is not as bright being covered by oxide and the
inside of the glass willl have been blackened by deposition of, again,
oxide. Tis the way of all incandescent bulbs - except halogens where
the halogen cycle (for the most part) solves this problem.

The bulbs were ~ 20 years old. When was the last time you got 20 years
out of an incandescent bulb? :-)

Also do not underestimate how much the film of whatever it is on the
inside of the cluster bezel cuts down light. Clean that up and it
makes quite a difference.

Signature

Reply to this Message

Tiger - 01 Aug 2006 20:12 GMT

I think that is what is missing... the cluster bezel that allows the light
to shine into the cluster. I had new bulb... hooked up the speedo directly
when out of the cluster... real bright.

Reply to this Message