Instrument Lights in Dash - no backlights

[dtuttle123]

All my instrument (back)lights in the dash(Speed/Tach/Oil/etc.) are not working - it's either a problem with power to these lights, or the lights have burned out, and have not been replaced.  Since getting into the instrument clusters and dash is such a pain - any advice as to what to check next?  Are there individual bulbs in each of the three instrument clusters, or a single illuminating source?  My car is a 1967 250SL.

Thanks for any advice!  Doug

[glennard]

Fuse(s)?   Reostat has a habit of corroding up.

[Douglas]

Chances are, the dash lights are just out of adjustment. It's tricky to reset them, but it just takes a little fussing. When I have this problem, I usually drive at night and turn that knob until the rheostat catches. Then, make sure never to touch that knob!

Douglas Kim
New York
USA

[BHap]

i had a shop bypass the rheostat - they said it was no longer available - i have dash lights, but no adjustment......

Bob Happe
Pittsburgh, Pa
1970 280SL, white/black 4 speed

[joelj]

I do what douglas does. Just turn it until it works. I have another friend who goes to the junk shop and takes the rheostat of old Mbenzes since he said that this is no klonger available. I did not beleive himthen but Iguess he is spot on.

Cheers

Joel

1969 280sl auto
White exterior
Blue interior

[Jonny B]

The lights are dim even when full on, so bypassing the rheostat is not that much of a sacrifice.

If the bypass, or fiddling to get the sweet spot does not work, the next thing to check is the ground strap (brown wire) that is connected at the back of the speedo/tach/instr pod. These sometimes are not put back in place. There may also be a short in the wiring or the connections, or with the keeper (the u shaped bracket that holds the different instrument in place. If the keeper is making contact with one of the wire or bulb connections, that can be a problem.

Jonny B
1967 250SL Auto

[dtuttle123]

Thanks everyone!  I'm sure it's the rheostat, and now I have a few options!

[userzweig]

I have the same problem.  My lights used to work, but once I hit a bump and they all went out for a few months.  Then, I hit another bump and they came back on.  Then, I had some body work done, and they went out again, and they've been that way for about 6 months.

Any ideas about what might cause this?  Playing with the rheostat does not seem to help.  I think they've gone off and on about 4 or 5 times, usually due to hitting a bump in the road or some body work.

Bruce

1971 Copper 280SL Automatic

[rwmastel]

quote:Originally posted by Jonny B

If the bypass, or fiddling to get the sweet spot does not work, the next thing to check is the ground strap (brown wire) that is connected at the back of the speedo/tach/instr pod. These sometimes are not put back in place.

Bruce,

Hi.  Maybe it's the ground wire mentioned by Jonny?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[burney]

your rheostat dimmer switch sounds faulty

[Ulf]

I also bypassed the rheostat - it was surprisingly easy and all my lights came back on immediately, no way of turning them down though, but who cares?

[Garry]

Just tonight my dash lights flicker and fail.  Checked fuse but it is ok, shook nob of dimmer and they came on for a bit and failed again.  

Ulf, care to give a bit of a speel on how you bypassed the rheostat and also the grounding wire, where is it attached back there?  I have a blanking plate on so relatively easy to access part way there.

Garry

[Naj ✝︎]

Garry

Check this thread:

http://www.sl113.org/forums/index.php?topic=12303.0

Post #10 by al_lieffring

Naj

[Garry]

Thanks Naj,  Will try Al's jump of the two terminals this weekend.

Garry

[Ulf]

Yes Garry - I used that exact thread and it's also covered in the tech manual I think - didn't even have to solder it as things are very tight in that little box (the one nearest the steering wheel btw)

:-)

[Jonny B]

This was also detailed in one of the Pagoda Notes issues, with the photos. Volume 4 number 3.

[Garry]

Followed Al's instructions and added the bypass wire but alas no instrument lights.  Checked fuses including No. 7 but all are ok.

Any other suggestions?

Garry

[J. Huber]

Garry, are you certain the brown ground wire is attached to the tach? Also that the bulb housings are firmly seated in the instruments.

[twistedtree]

And is battery voltage present in the connector on the terminals where you added the jumper?

[Garry]

Todays jobs, put a voltmeter across the terminals and check on the earthing wire..  As it spluttered to darkness the other day, the earth wire could be a problem although it was ok when I was in there a week ago.

[Garry]

Pulled out the plug under the dash and checked yesterdays handiwork and put the voltmeter on the link and no power, checked fuse and noted this time it was failed.

 Put a new fuse in and immediately blew.  Checked earthing wire and all ok. then remembered that I had a problem with rear right tail light last week and as that was also on the same fuse (7) decided to check if something there was the problem. Pulled out the rear tail light and there lay the problem, a wire loose causing a short. fixed that put in new fuse and now dash and tail lights working again.  As I have bypassed the rheostat I think I will leave it like that as there are very few times I drive at night and the lights are relatively dim anyway.

Now next item on the list for the weekend jobs.

Thanks all for suggestions. A bit of practice for the classic Lucus electrical problems to be encountered on the Jag, I am sure

Garry

[twistedtree]

Thanks all for suggestions. A bit of practice for the classic Lucus electrical problems to be encountered on the Jag, I am sure

Yes, practice makes perfect, and you'll need all the practice you can get    Sorry, as a former E-type owner I couldn't resist.....

[71Beige280SL]

Here is one for the group. I have the tach and center instrument cluster lit up just fine. The speedo is very dim, almost dark. Rheostat has no effect. Suggested fixes?

[Larry & Norma]

Bulb has blown or holder has fallen out of back of speedo maybe.