W123 Dashboard Lights

[jaco]

All of the dashboard lights on my W123 are dead. Cannot read what speed I am doing at night, etc. Tried pulling the cluster and cleaning the rheostat, but to no avail. I even tried (as an experiment) to bridge the rheostat with a piece of wire. Didn't help.

Now I know there is a relay of some sorts on the back of the cluster. Can anyone perhaps identify what this relay is? Could this have anything to do with the non-functional lights?

 

[Ted]

No, the dash lights are not controlled by a relay.

Do you have a supply to the rheostat? Do you have a supply OUT of the rheostat? - Use a test lamp.

If yes, it is bulbs, or less likely pcb.

If no, it is most likely the supply - do all of the sidelights come on?

 

[jaco]

When you say sidelights, do you mean the lights on the outside? Yes they all work.

On my way to the library now to go get a wiring diagrahm from the Haynes manual (or whatever they have) to check the supply at all the locations.

 

[jaymanek]

on the back of the rheostat simply bridge the two connections with a piece of wire. If the lights come on you know what the problem is.

 

[Ted]

It's a long time, but iirc, the right hand sidelights are grey with a red tracer, and the left hand sidelight is grey with a black tracer. The dash feed will probably be one of these, but will almost certainly be grey with a tracer.

And while you're out, buy a test light.

 

[219]

Or better still , a multimeter !

 

[Ted]

Test light is better for tracing this type of fault.

A multimeter is better for voltage specific issues (charging etc) or current realated (permanent discharge, charging)

 

[jaco]

Gents,

First off I would like to say thank you for the way thsi community makes even a newbie feel welcome.

Now down to business... I removed the instrument cluster and started testing the reostat and things. (The box that looked like a relay turned out to be a buzzer.) Tried a bridge over the two terminals of the reostat - no go. Then, somehow... Blaas ek die bliksemse bord... Sorry... I blew two tracks on the board (nfi how I did that). Now, whenever I start the car and switch on the lights, The fuel guage shows the tank is half full (wouldn't it be great...)

Anyway, I'll be getting a new cluster housing (to fix the lens I broke last time I removed the cluster) and multi-gauge assembly from German Auto Spares (local 2nd hand Merc parts specialist) a little later in the week. Maybe that would solve the lights issue? (Then it's off to have the busted CV seen to, and to get the blower operational before the cold sets in.)

 

[billyboy88]

dashboard lights

I have got the same problem, no dash lights or interior lights, everything else works like the electric windows, and all outside lights.
the clock and the economy gauge isnt working too.

I presume this is a dashboard out job, dont think i am that brave to do this suppose i will need to see a specialist mercedes garage?

 

[Ted]

Try turning the dimmer switch from endto end a few times.

 

[billyboy88]

Try turning the dimmer switch from endto end a few times.

Can you tell me where the dimmer switch is in car, the only switches i have on the dashboard are the trip meter stalk and the clock stalk.
On the centre console is the headlamp switch and heat rear window.

 

[jaymanek]

its the mileage trip meter reset button, turn it side to side.
The best thing you can do is remove the cluster, find the rheostat (small white square thing) and put a piece of wire across the pins. This way your lights will be on full brightness and you will never have the problem again.

 

[billyboy88]

Can you tell me where the dimmer switch is in car, the only switches i have on the dashboard are the trip meter stalk and the clock stalk.
On the centre console is the headlamp switch and heat rear window.

I can now answer my own question!
The dimmer switch is also the trip recorder stalk control