123 and 126 dash lights problems - PeachParts Mercedes-Benz Forum

b52rule · #1 03-31-2008, 07:51 PM

Gents,

Can someone lead me to or send me pics of the results of using higher than normal light bulbs in the earlier (early to late 80's 123's and 126's)? I understand it melts or burns the plastic optics.

Thanks

B52Rule

Erlend · #2 03-31-2008, 08:58 PM

My experience has been that the PO had 5W instrument cluster general illumination bulbs where there should have been 3W (194 style bulbs). The result was seriously melted and deformed prisms adjacent to the bulbs and some melting/warping of the white plastic that surrounds the bulb. The latter is often evidenced by light leaking over to the turn signal light area so that they appear partially on all the time.

My solution was to find a good used instrument cluster with good prisms and good white plastic surrounds (eBay) and then stay away from 5W bulbs.

I have since done some experimenting with lower wattage LEDs, with mixed results. One attempt seemed promising, but the illumination angle of 35 degrees was not adequate to reach the prism, which is not straight ahead of the bulb (I think it is higher). This attempt using LEDs from www.superbrightleds.com (30 mA at 12V, so very low wattage)

Another attempt was with an SMT surround light LED from www.ledlight.com. These put out 1.5W, which is a lot for an LED in this usage. Unfortunately, I tried these not knowing that my prisms were already melted. When I get around to it, I'm going to try again with the new cluster shell and prisms.

General conclusion to date: the prism and light tunnel design sucks and there is not a whole lot you can do about it.

hangit · #3 04-01-2008, 09:27 AM

I have used the LED lights in both my 240D and 300SD with good results. After cleaning the prisms with alcohol/windex, I lined the cavity that surrounds the bulbs with reflective aluminum tape. Verify that the tape does not contact the circuit wiring. Much brighter than stock.

John

Cr from Texas · #4 05-31-2008, 01:36 AM

I've been replacing the original burned out baseless bulbs (3W?) in my 123 CCU. I think they are the original ones and I have some minor issues with melting near the bulbs. The bulb behind the headlight switch looks the same but is frosted (no melting). I can not find any markings on the bulbs. Are the frosted ones lower wattage?
Where can you buy the frosted type? I'd rather have dim lights if it avoids the melting.

daw_two · #5 05-31-2008, 08:41 AM

I don't know if I still have the pics, but "Elegant Madame" had melted plastic and browned light tunnels. The picture below is from a parts car. Any questions?

Chad300tdt · #6 05-31-2008, 09:00 AM

Check this thread for links to the LEDs needed:
http://www.peachparts.com/shopforum/showthread.php?t=213844&highlight=LEDlight.com

I am very happy with the results, but my prisms are clean and in good condition and I used the silver tape as well. BTW, I put all new, stock wattage incandescent bulbs in my CCU and they melted the socket for the temp wheel. I am now replacing those with the 74 Wedge Base LEDs to keep any more melting from happening.

On a side note: After replacing my dome lights with LEDs, I accidentally left the front dome light on overnight. The next morning the battery was fine and didn't need a jump or charge. Another benefit to using low power consuming LEDs.