Dashboard/Instrument lights

[Asper]

I have just bought 1968 280 SL. All lights are working except the dashboard/instrument lights. Interior light and glovecompartment light are working but not any lights in the dashboard. Have anybodu experienced a similar problem?

Kjell Asper, Norway

[66andBlue]

Have you turned the rheostat completely clockwise?
See: http://www.sl113.org/wiki/Electrical/Rheostat

[w113dude]

The best thing to do is bypass rheostat by soldering a single link, I don't ever remember dimming my lights on any of my cars for any reason what so ever, so what is the use of this thing anyway?

[Asper]

Thanks guys. I have tried turning the rheostat back and forth with no succes. Do I have to take it out to bypass it, or is there a better way to do it?
Kjell Asper

[w113dude]

Kjell,

I did mine while back, but to bypass the rheostat you have to connect the two connection that go to it with a single wire, power is going through rheostat and it's being adjusted by that little knob what you want to do is by bass it by so the light stays on & you don't have to take the unit out of the cluster, If you can wait a week or so I might be able to do one in a used cluster it with images and post them on the forum.

[Asper]

Shaun,
I appreciate your information. No problem to wait a week or two.

[w113dude]

Here is how to bypass the rheostat on your cluster so dash lights always stays on, this is in a case where you don't want to replace your rheostat, 
All you need is a piece of electric wire and a soldering gun. We are essentially connecting the two wires that go in to and come out of the rheostat, take a look at the images for simple directions.

Cheers
Shaun

[Cees Klumper]

... I don't ever remember dimming my lights on any of my cars for any reason what so ever, so what is the use of this thing anyway?

I always dim the dash lights on every car I have - actually the Pagoda is the only one where the lights are already so dim, they don't need additional dimming. The reason I dim the dash lights (and sometimes even turn them off completely) is because it diminishes the quality of my vision on the road.

When I am in a taxi in the evening, I tend to note that the dashboard lights are brighter than I would have them ...

[w113dude]

I always dim the dash lights on every car I have

I agree, on modern cars the lights are very bright, since all my cars have always been Mercedes Benz I have never had any need for them! (a bit of clarification)

[Asper]

Thanks Shaun. Looks simple. I appreciate your help.
Kjell

[al_lieffring]

As I was reading through this thread, I realized that Shaun's rheostat jumper is a perfectly good procedure, but it can be made even better by eliminating one "small" step. You don't need to remove the center cluster from the dash board.
The other end of those two wires are accesable from under the dash at the 12 prong plug next to the steering column. There are 2 - 12 prong plugs on the metal bracket that the flasher can also hangs on, one for the turn signal combi switch (marked with red tape) and the other goes up to the center instrument cluster.

By taking the cover off the back of the male plug (3 screws on a 230, snaps off on 250 and 280's)  you will then be able to remove the two wires that go up to the rheostat. One is grey w/violet stripe the other grey w/blue stripe. Hold each terminal pin with a pair of needle nose pliars, heat with a soldering iron untill the wire pulls out. While the solder is still hot tap it aginst the floor and the excess solder will come out and clear the holes.

Make a short (insulated) juper wire and solder it with the original wires in the terminals, replace the terminal pins back in the plug where they came out, reinstall the cover on the back of the plug. plug it in and check for operation of dash lights.

I took these photos on the workbench, but the job could easily be done in the car sitting in the driver's seat, with the steering wheel removed.

[w113dude]

Al, you're the man good job.

[wd]

AL,
  Are the pins easily removed and replaced in the plastic?   

   I did my coupe rheostat some years back.  I used 10 or 12 gauge tinned marine wire.  I did not solder it and wonder if that is going to be a corrosion problem down the road?  After taking the back off I cut a short piece of marine grade wire and while waiting for the soldering gun to heat up I tried fitting it into the holes in the head of the post that the wires solder to.  The fit was absolutely tight.  So I bent the little loop over and put the cover on and so far so good without any soldering.  May need to do this soon on the sl so wondering about the first question as to the pins removal and replacement?

[al_lieffring]

The pins are a loose fit in the plastic ,there are no barbs like weather-pac terminals, the rear cover holds them in place.

Corrosion shouldn't be a problem if the wires are soldered.

[twistedtree]

I just implemented this bypass at the connector plug as described.  It took about 30 minutes all told, including finding my soldering iron, etc.  Beats the heck out of removing the instruments (I couldn't even get the tach cable or mounting knob to turn).  Now I have dash lights!

Many, many thanks.

[al_lieffring]

Glad to hear that one of my crazy ideas actually does work out in the "Real World" I have a tendency to think when I see something as obvious that means everyone else does too.

[Peter van Es]

Now can someone add Al's excellent procedure to the Tech Manual ?

Peter

[bpossel]

Peter,

Done!

Bob 

[Chrisheg]

Another adventure in old car ownership :

I had the same problem with no instrument lights so I went in to see what the problem was. Turns out that the two rheostat wires had shorted to the point that they completely burned off their insulation through the entire cable bundle, fusing all of the other wires together with melted insulation and cable jacket. I managed to dissect the cable and repair the other wires, then cut out the two bare rheostat wires and jumpered the pins together. Now everything works except the center instrument cluster lights. I will have to pull out the instruments again to fix that. Should be easier the second time. 

[abe280SL]

Ever stop to think that some german dude (dead or retired by now) back in the late 60s was working hard making those components and placing them in our car....and here we are undoing everything that man (or woman) did for us?
Just a thought...since I really don't have much else to add. :'(
abe

[Peter van Es]

Peter,

Done!

Bob 

You're a hero!

[280sl1968]

Does anyone know if any of the later VDO rheostats can be used as a replacement?

[al_lieffring]

no they are not the same, but most of the internal components are the same as the reostat in the 108 and 115 dash clusters. to get the reostat apart the brass rivets would have to be drilled out.

[Till]

Hi Guys,
Every time I switch my headlights on, my fuse #7 pops! I have traced the problem to a shorted rheostat in the centre light console, i.e. there is a direct short circuit between the two pins 5 and 6 (and the two connected wires to them). I can only assume that the resistance coil inside the rheostat itself is somehow causing an internal short to its casing (which is of course grounded!)
In order to stop the fuse popping, I de-soldered the + wire inside the 12 pin plug underneath the dashboard, with the result that I can switch my headlights on but the dashboard lights are off!
I could take out the centre console, de-solder the three wires off the rheostat itself and solder them together, thereby isolating the rheostat completely.
I would rather replace the rheostat with another, either with an original or possibly a modern version.
Does anybody maybe have a few spare old rheostats or possibly know of a modern replacement?
Regards Till

[al_lieffring]

Usually a short in the dash pannel lights is caused when U shaped brackets that hold the speedo and-or tach are improperly installed and touching a hot contact on one of the 4 light bulb sockets. Or if you are not finding any thing there, unplug the clock and the lights in the heater levers. and finally the two illumination bulbs in the center instrument cluster.
When the reostat fails the dash light circuit goes open, it is very unlikely that it is shorting to ground, the reostat housing is a soild block of ceramic, almost no metal to contact ground anywhere.
There are some wires crossed somewhere else in your dash light circuit, but the reostat jumper was done to remedy a different problem. I can not recall a time that the 113 reostat was ever sold as a seperate part, maybe it was 30 years ago or more.
Some time soon I plan on writing up a procedure to repair the pagoda reostat by using components from the (fairly common) 108 or 114 sedan dash cluster's reostat.