I would like some help on this as well, as the dash lights on my newly purchased 280sl are out as well. Everything else works and the fuse is good.

 

The rheostat has two wires and they need to be shorted together. There are many ways to do it. Bottom line is that when the rheostat is in the bright position, the two wires that go to it are shorted together or 0 ohms across.

 

I just refurbished the instrument cluster for my 72, maybe I can help.

If you want to replace the long socket, the part number from EPC is:
A 000 545 16 19

You should be able to get this from your MBZ dealer, maybe some of the internet places would have it because it's not specific to the 107.

The power for the instrument cluster comes in through the main connectors for the cluster, then is distributed to the instruments and the lights via the circuit boards for the multigage (left) and tachometer (right) sides. At the back of the cluster there are 2 red wires that run from the tops of each of the circuit boards to the potentiometer (dash light dimmer). These wires attach to the potentiometer via 2 90 degree spade connectors. I suppose that you could jumper these 2 wires together and have the dash lights on bright all the time. To find out if you have a potentiomer problem, you could replace all the bulbs with new ones, then jumper the potentiomer, and if the lights come on, you can decide if you want to spend the $80 or so on a new dimmer.

I replaced my potentiometer because when I took the cluster apart I saw that there was a lot of ceramic dust in an around the area of the potentiometer. This was from the body of the potentiometer and showed that there was some significant deterioration of unit. I had a problem with the dash lights not working at the end of the travel (brightest), but I could jiggle it around and get the lights to come on.

I pulled the cluster to get the speedo repaired, which had a bouncing needle, and also to replace the oil pressure gauge, which had been seeping oil for many, many years. When the cluster was disassembled I got a plastic polish kit from Eastwood Co and took about 2 hours to polish all the plastic pieces, especially the clear cover. Now it looks like it did when it was brand new, except the odo say 130K.

I've got some photos of this but am on the road now and can't post them until I get back home on Saturday.

 

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The power for the instrument cluster comes in through the main connectors for the cluster, then is distributed to the instruments and the lights via the circuit boards for the multigage (left) and tachometer (right) sides. At the back of the cluster there are 2 red wires that run from the tops of each of the circuit boards to the potentiometer (dash light dimmer). These wires attach to the potentiometer via 2 90 degree spade connectors. I suppose that you could jumper these 2 wires together and have the dash lights on bright all the time.

Have my 1972 cluster out at present. Just wanted to correct the part highlighted above. The tab that those two red wires connect to is a common tab so those two wires are connected anyway.

The power comes into the dimmer via pin that sticks out of the back of the cluster and can't be seen unless dimmer is removed. That pin connects to a brass strip on top of dimmer adjacent to tab that those red wires connect to.

To jumper the dimmer need to connect the double tab to that brass strip.

 

Thanks for all the info, especially the part number for the long tube. But I had a pretty good afternoon working on the cluster. I finally figured out how to get the cluster completely out of the dash. once I had it out I was able to take it completely apart, I found the tip of the long tube with the lamp still attached stuck in the front of the cluster where it should be. I then took the left turn signal small socket apart and used the spring and slider piece to repair the long tube. I ordered new LED lamps last night but obviously they hadn't been delivered yet so I cruised down to Manny Moe and Jacks and picked up two 2 watt incandescent lamps. I used electrical contact cleaner on the circuit board and the lamp sockets then I put it all together and it works great I don't even think I'll need the LEDs but they do burn colder and last longer so when they come in I'll do it all again. The good news is that the Rheostat seems to be fine

 

Chas, where did you get the LED lamps from?

Thanks
Damian

 

I havent received them yet so I'm not 100% positive that they will work correctly. I ordered them from LedLight.com
I'll post when I receive them.
Chas

 

Lets hope they do after all the trouble to get them on.

 

Any update on the LED lamps? Any photos of the process?

My dash lights are also not working, but all the gauges are working fine. I'm hesitant to take it apart without explicit instructions for fear I'll damage something. But driving at night is much less interesting without lights!

I tried to adjust the dimmer, but it caved into the dash and now I can't get to it or rotate it.

Has anyone used deoxit on these components? I have used deoxit successfully to clean potentiometers on old stereo equipment (Hobby #2). But not sure if Merc dials are too sensitive?

Thanks in advance!

 

Cluster removal and takey aparty:

http://www.benzworld.org/forums/r-c107-sl-slc-class/1495136-odometer-repair-tutorial.html

Lights:

http://www.benzworld.org/forums/r-c107-sl-slc-class/1535184-cure-dim-turn-signal-indicators.html

 

On the reostat if you drill out the rivets you can open it, clean and reassemble with 2 small nuts and bolts. I have a spare if yours is broken along with most of a disassembled cluster.

 

Assuming your car has one check to make sure the star cluster/connector is on tight. Mine was loose giving me fits. Pic 8 in #2.

http://www.benzworld.org/forums/r-c107-sl-slc-class/1495136-odometer-repair-tutorial.html

ps...I was able to get my hand up there by removing the speaker.