W126 Instrument Cluster Light Guide - PeachParts Mercedes-Benz Forum

wgilmore · #1 02-23-2009, 01:33 PM

I want to improve the illumination for my old 86 300SDL and was wondering if anyone has come across an instrument cluster for a later model 126 chassis and noticed the light guide as to whether it is the same as the 1986-87 style.
Below is an image of a 1986 light guide.
Really don't want to do a lot of work on this if anyone knows of a MB improvement in the W126 chassis like that in later W124 instrument cluster lighting.

oldsinner111 · #2 02-23-2009, 02:20 PM

I've read that cleaning the dimmer switch for dash lights really fixes things.CRC electrical contact cleaner (safe for plastics).

wgilmore · #3 03-01-2009, 12:49 PM

Quote:

Originally Posted by oldsinner111

I've read that cleaning the dimmer switch for dash lights really fixes things.CRC electrical contact cleaner (safe for plastics).

Done all of that , replaced bulbs , added foil tape, cleaned back of light guide , cleaned white markers, re-painted pointers. Still not bright enough for my eyes.

Surely someone out there must have seen the light guides in a 350SDL or 350SD or in a later 126 gasser that is compatible with my cluster.
Just need to know if the light guides are different from the image in the first post of this thread.
My local salvage yards rarely get later model stuff, just the older cars, haven't seen a 1990 + car in some time.

freeride · #4 03-01-2009, 01:18 PM

You will be amazed what LED will do. There is a thread about this. I just got some blue LED's for my dim cluster in 300SD and it looks like a space ship, nice and bright

http://www.ledlight.com/t10-wedge-5-ultra-bright-smt-led-light.aspx

wgilmore · #5 03-01-2009, 01:51 PM

Quote:

Originally Posted by freeride

You will be amazed what LED will do. There is a thread about this. I just got some blue LED's for my dim cluster in 300SD and it looks like a space ship, nice and bright

http://www.ledlight.com/t10-wedge-5-ultra-bright-smt-led-light.aspx

I have seen several of the different types that will fit in the wedge base socket.
I really wanted to used a true white LED since to my old eyes , blue is very distorting . Most of the low cost LEDs in white have a color temp of 7500* K to 10,000* K (or higher) which gives a strong blue shift.
If I can find out if the later 126 chassis have an improvement to the light guide, then I might be able to simply use a single 4500* K 0.5 W or 1.0 W LED in the area where the bulb goes.
Otherwise , I will have to cut the existing guide and use a strip of 5-10 SMT 100 mW LEDs at the point where I cut into the light guide. This I would prefer not doing.
THanks for your input.

dcotejr · #6 03-01-2009, 08:56 PM

I was having alot of trouble seeing the instrument cluster on my 81 300SD at night (Probably somewhat age-related;-)). Just replaced the bulbs with bright white LED's (see web link above), and I can see everything perfectly after the sun goes down. Very inexpensive and simple fix...

Don

#7 03-01-2009, 09:20 PM

+1 on the LED, they have LED bulbs on eBay for like $2 each. I have begun to replace each bulb one by one with LED bulbs. I am liking the bright white look. It is also nice to know that I may never.....ever.... have to replace them again. If your looking for a specific color temperature. The eBay stores Ive seen sell different temps. They even sell an amber LED if you are looking for that classic orange-ish look.

Johnny K · #8 03-01-2009, 10:06 PM

1986 300 SDL, I want to replace them with white LED's. What is the LED bulb called? ANd I think I need two for the dash lights ? Thanks for the help

John

wgilmore · #9 03-02-2009, 12:56 AM

Quote:

Originally Posted by Johnny K

1986 300 SDL, I want to replace them with white LED's. What is the LED bulb called? ANd I think I need two for the dash lights ? Thanks for the help

John

Some places call them W3W or Wedge Base or T3-1/4 or T3.25 or 2721 or 194 or 168 .
I would search for wedge base and T3-1/4.
You will want something that has LED's pointing upward toward the light guide .
There is a type called a "flank" LED that has all of the LED's on one side of the PCB pointing in one direction.

hangit · #10 03-02-2009, 12:38 PM

How long have the LED's lasted? I purchased some from an Ebay supplier and they burned out after 5 or 6 months. This happened in both my 240D and 300SD.

John

wgilmore · #11 03-02-2009, 01:05 PM

Quote:

Originally Posted by hangit

How long have the LED's lasted? I purchased some from an Ebay supplier and they burned out after 5 or 6 months. This happened in both my 240D and 300SD.

John

Yes, this is the problem I have seen as well. The "High Power LED's " do not have proper capacity to dissipate heat and no external convection path. The normal low power LED's claim they have a color temperature of 5000* K, 6500* K etc.. or some such correlated CRI , but in reality are way off from that.
Since I can't find out if the later W126 chassis have a light guide improvement, I will be making my own upward emitting 0.5 W "High Power LED" that will plug into the W3W socket and have proper cooling and a true color temp of 4500* K. I have tried and/or seen all that is out there and I just don't want them.
There are only 3 manufacturers of accurately rated high quality led die.

freeride · #12 03-03-2009, 12:08 AM

Ok I took some pictures to show my improvement, don't have old pictures with regular bulbs but believe me it was dark.

First picture shows the kind of wedge I ordered, there is LED on 5 surfaces and each surface is made of 3 tiny LED's, too small to see on the picture

Second picture, only looks dark on the picture but wonder why right side (RPM) is brighter? Go to 3 to see what I did

Third shows the casing surrounding the bulb, it's white or rather yellowish after all the years. I covered one with aluminum foil (shiny side) to see the difference. There is big difference, aluminum (or silver paint would work too I guess?) reflects the light so much better than white plastic...

Then final which still looks darker than reality but it's hard to take good night picture with point and shoot camera.

I am sure white LED would be brighter but this is plenty bright for me, I just wanted something cooler looking. I am sure aluminum foil would improve things even with stock bulbs. If You do it, don't forget to glue it all around the bulb (that is half on removable casing and half on the speedo case) and use one slight drop of Loctite (super glue)

bigfredb · #13 03-10-2009, 01:27 PM

My lights just burnt out in my '83 300SD.

How many lights are in the instrument cluster (so that I know how many to order)?

Does anyone have the electical layout of the instrument cluster that they could post? I am having some other intermittant light problems as well and wanted to make sure they werent related.