W124 mirror switch illumination DIY repair - PeachParts Mercedes-Benz Forum

Jeremy5848 · #1 01-12-2009, 02:16 AM

Previously it has been mentioned in this forum that the adjustment switch for the passenger-side mirror is supposed to be illuminated. I didn't know that and first checked the schematic diagram in the ETM. Sure enough, S50, the "Outside Mirror Control Switch," was shown with a lamp. Then I pulled a spare switch out of my junkbox and disassembled it. Yep, there's a tiny lamp inside, burned out, of course. Replacing that lamp is the subject of this DIY.

The lamp in question is commonly referred to as a "grain of wheat" lamp and that's about how big it is. (This is a job in which tiny fingers are really helpful.) These lamps are often used in military equipment (where they are usually 28 volts, no help). You can sometimes find them in 12 volts at surplus electronic stores and that's where I found mine.

Taking the switch apart requires several small screwdrivers because there are six plastic tabs that hold the bottom in the case. Carefully spreading the case apart will allow you to pull the bottom out. Be careful! As you can see from the first picture, the switch is full of tiny parts. In particular, the three "dumbbell" electrical contacts and the six springs would easily disappear if dropped.

With the switch apart, you can see that the bulb is soldered to the base. Using a tiny soldering iron, remove the old bulb and solder in the new one. Note which pins on the base are for the bulb. Test with 12 volts to make sure the new bulb actually works, then reassemble the switch. The base is polarized so it can't go in backwards. The white plastic thing that holds the springs and the dumbbells likewise can go in only one way or there won't be a space for the bulb. Test again and return the switch to the car. The last photo shows the switch in a dark room with the center spot illuminated. It doesn't make a big glow, just enough to allow you to find the switch in the dark.

Jeremy

pawoSD · #2 01-12-2009, 11:40 AM

I think I'd replace it with an LED....after seeing how much fun taking that apart is!

A yellow LED would give essentially the same color dot....

Jeremy5848 · #3 01-12-2009, 02:42 PM

If you can find a sufficiently small LED that will operate directly from 12 Volts, please let me know, that would be a great and hopefully permanent fix. Another option would be to build a dropping resistor into the cable feeding power to the bulb.

compress ignite · #4 01-12-2009, 03:24 PM

Jeremy 5848,

Excellent definition in your pictures.
(I tried but couldn't do as well)

A little dab of Vaseline on the Ball parts of the "Doggie Bones",
holds them in place on top of the springs whilst you install the top of the
switch.

Radio Shack
Micro lamp
#7219
12 volts 60mA
(In a two pack)

PawoSD,

Please let me know the brand and part number of the LED you eventually source
for this application...I "Been Looking" for months without success.

Jeremy5848 · #5 01-12-2009, 10:00 PM

Quote:

Originally Posted by compress ignite

Jeremy 5848,

Excellent definition in your pictures.
(I tried but couldn't do as well) . . .

Thank you, there's a lot of Photoshop in those pictures!

and it's especially hard to get a picture of the illumination, since it's so dim. The camera has a built-in focus light for dark scenes; that's the only thing that saved the fifth one. Almost impossible to illuminate the switch without drowning out the internal bulb.

Here's a picture of the console with the re-bulbed mirror control installed and the lights turned on. The push-switch at bottom center is for my garage door opener. I don't like drilling holes in things where they show but the PO already had something there so the damage was done. I recessed the switch so it can't get accidentally depressed.

Jeremy

Renntag · #6 04-10-2010, 03:13 PM

I just dove into this project with the purpose of removing years of gunk making the switch sticky and nearly inoperable. After completing the task with success, I decided to search for a DIY and make one if there was not something already.

Nice job.

I would like to add that I also removed the handle from the center by sliding it up. This enabled me to better clean the valley under the handle and also push out the clear pin that transfers light from the bulb to the spot on the handle.

Cleaning the socket the pin rides in solved the sticky issue. A dab of silicone grease made it nice and smooth. Additionally, I added a dab of silicone (di-electric) grease to the end of the spring/pin assembly that rides in the center of the switch. This also gave it nice smooth return action when fully assembled.

An LED would certainly be the ticket for this job and a resistor in the harness would work just fine.

I will take mine apart again to do the LED upgrade once I have an idea which one to use.

Sev · #7 04-10-2010, 06:35 PM

how much is your time worth to you? you can buy a used/working switch or even a new one online for less than the time it takes you to fix this switch

charmalu · #8 04-10-2010, 10:20 PM

Great job Jeremy, no matter what your time is worth

.

I need to pull one at the JY to see how close this is to the 123 for a swap.

Charlie

Sev · #9 04-11-2010, 01:29 AM

the illuminated side mirror switch came out in 1986 along with the w124. w201's got it, too. since later w123's after 1983 had the w201 side mirror switches, and since people with early w201's have been able to upgrade their switches (complete console switches) to later w124 style, therefore it's possible for 2nd gen w123ers to switch their switches to the newer 124 style. you need to get a pigtail of wiring along with the switch though. there's writeups on how to do it on the 190e forums

compu_85 · #10 04-11-2010, 01:43 AM

I never understood why Mercedes didn't just switch everything over to LEDs. The window switches use LEDs, some of the switches on the dash of my car still use the fiber optic hydra for nighttime illumination, except for the rear dome light switch which I suspect has an LED in it, and the fader wheel which has a bulb? The hazard switch uses one bright filament lamp with a resistor for backlighting... such an odd mix. Yet somehow the brightness and color of all of the switches is the same!

Yes, VW was doing the same thing in the 90s... in fact they still had a mix of LEDs and small filament lamps until the 4th gen cars came out in 98. My 99 Jetta has only one filament lamp in the interior excluding the dome lamps. I guess Mercedes didn't think LED technology was ready in the 80s? Not having half of your dashboard burn out is a nice selling feature IMHO.

-J

pawoSD · #11 04-11-2010, 02:18 AM

Yeah I have wondered that too....but it also comes down to cost....LED's were expensive as heck back then....so they probably did not feel like using 40 of them throughout the switches. You could probably use regular filament lamps in pretty much the whole dash for the price of one or two LED's.

I replaced a ton of my dash lights about 2 years ago, and a few are already burned out again....the first to go was my temp wheel on the klima....now that is just annoying! It was a brand new lamp!

compu_85 · #12 04-11-2010, 03:12 AM

Too expensive? That seems like a poor justification for not having something on a Mercedes, let alone the S-Class