One of the most frustrating parts of working on these w126s is the way in which Mercedes decided to light all of their console switches and instrument cluster. Being high tech, they went with a fiber optic system that delivers light via an external socket. Let me get more into detail here.
The two areas that people most often come in contact with these fiber optics is the instrument cluster and the center console. First lets tackle the instrument cluster. The cluster has long been a point of contention with Mercedes owners as these cars grow older, since the lighting becomes worse and worse until the driver (dangerously) cannot read the gauges at night. Problem number one is the rheostat. The springs that the company used in the rheostat fail pretty commonly. This results in NO lights whatsoever. I recommend jumping the rheostat, which consists of simply putting a jumper wire between the two solder joints on the board. If you want to do any LED modification or anything you'd have too do this anyways to help regulate the current.
The bigger problem with the instrument cluster is the delivery of light to the gauge faces themselves. The bulbs are located in the back of the instrument cluster next to the blinker bulbs. Easy to replace for sure, but if you look closely the light has to travel through crystals over the top of the plastic housing and then refract back down on the instruments. In the bulb sockets themselves, about 90% of the clusters that I have seen have black charring (presumably from long time burning of bulbs, perhaps incorrect bulbs?) on the face of the fiber optic prisms. I have also seen the prisms melted from having too hot of a bulb in there--obviously this doesn't help either. In addition, all sorts of dust can get caught in there and is very difficult to clean. My solution was to completely bypass the fiber optics in the instrument cluster and go with a homemade LED setup. I mounted the LEDs where the prisms came out to light the gauges, and soldered them back to the bulb sockets. The LEDs were actually far too bright so I had to shield some of the light with electrical tape...even that is still very bright, but that is my preference for dash lighting.
On to the center console. All of the switches on the top of the console except for hazard lights --rear reading lights, defrost, sunroof, and antenna (may be more depending on options) are lit by means of fiber optic cables in back of the dash. There is one light strand, much like a christmas tree wire, powering all the climate control and switch lights. I believe these are wired in series so if one bulb goes out, the following will also go out. There are 4 bulbs located in the climate control unit (I will get to that in a second) and one bulb reaches back into the firewall to a cluster commonly called either and octopus or a spider. The fiber optic wires coming off of it go to each of the top switches, and one goes down into the shifter console to light the PRNDSL selection. Conveniently, my octopus was completely torn apart by the previous owner who pretty much scrapped the whole interior. After many hours of toiling I recommend just forgetting about it, you won't easily get those fiber optic cables back into the octopus--it is so far back against the firewall, it gives almost no room to work, especially for a precise placement of these wires.
Back to the light strand. The first two bulbs on the strand light the left side of the climate control--the wheel and left couple buttons. Then, the strand reaches back to the firewall where ONE bulb (stock bulbs are pretty dim) lights all of the switches and center console, then the next two bulbs return to the climate control to light the right flap buttons and fan speed/auto buttons. Since I gave up on the octopus, none of my switches light up except for the hazard lights, and I replaced my climate control bulbs with LEDs to compliment the blue feel of the car. Any questions please leave in comments section. Thanks!
Showing posts with label lighting. Show all posts
Showing posts with label lighting. Show all posts
Saturday, April 9, 2011
Wednesday, December 29, 2010
W126 LED taillight project
I wrote this up for one of the forums but it went underappreciated...it is definitely useful however, so it will live in eternity on my blog, woo!
A common criticism of driving an old mercedes (particularly a diesel with a cloud of black smoke behind) is the lack of visibility at night. I can always pick out a w123 or w126 from a distance because of the dimly lit, downward-facing running lights. Stepping on the brakes does not do too much either, unless you are blessed with a third center brake light. With that in mind, I realized that there was a large portion of the w126s taillights that are NOT being used at any given time. There is the inside red lens where the euro fog lights would go (but U.S. versions have nothing) as well as only half of the main red area being used for running lights. Since I have a spare w126 laying in the yard, I took one of the tails off of it to experiment and this writeup is a result of that experimenting. I have a working prototype and will be converting the other taillight as soon as I can run down to the parts store for another LED light. Advantages of this LED light setup:
Disclaimer: I am not responsible for any harm or damage as a result of your following these directions. I am not implying or expressing that these taillights may be street legal in your local area.
Ok, so here is what you need:
- figures 1.1, 1.2: a DOT-approved 3 prong LED taillamp from NAPA, the type that you see on trailers and trucks. Cost about $25 if I remember correctly. Mine was about 3.5" diameter, filling up the whole red area of the tail light
- w126 tail lamp assembly
- soldering iron plus flux, shrink wrap, solder, and bullet-type electrical pins
- some way to cut plastic. Doesn't need to be pretty. I used a dremel with a variety of tips
- super glue
- about 1-2 hours of time
1. Completely disassemble the tail lamp. You'll have to separate the gasket (good time to replace it too), lens assembly, "reflector" assembly, and the metal strip with light sockets.
2. cut out room for the LED lamp in the reflector assembly. This takes some time and patience to get perfectly right. I got it after about an hour of trimming. You have to make sure to take the middle light separator out. Interesting note is that the plastic is crudely painted "reflective" silver. I can't imagine it doing much good in terms of light reflectivity.
3. Eventually get the LED snug in the reflector assembly so that it presses up against the lens/refractors (figures 3.1, 3.2). A couple dabs of super glue to the reflector assembly will make sure it doesn't go anywhere. Secure the screws to the lens, making it all one piece again. A good idea to test out the LED on a car battery for proof of concept (figure 3.3)
4. Wiring! Everybody's favorite thing! Actually it couldn't get ANY easier than this. First off, take either the bulb socket for the running lamp or the taillight and snip the wire off of it. Put that bulb socket in the "blank" space, where the euro fog light would go. The LED bulb I had already had the appropriate connections molded into the plastic: "tail", "ground" and "brake".
5. Plug it in and try it out! (Figure 5.1) See the difference--I apologize my camera is NOT good at taking night shots so it is difficult to see. The camera actually makes it look a bit worse than stock but I can guarantee you in person the difference is dramatic. Remember that LEDs produce one wavelength of light and bulbs produce a spectrum, I think that whatever the wavelength is for these LEDs is not well reproduced by my cheap camera whereas the spectrum is sort of a "flood" of light. Anyways, I noticed the normal taillights are not only pointing down and using 1/4 or so of the available space, but they are also amber colored. Using the LEDs brought light to the entire surface including the part FACING drivers behind you, and they light brighter as the brakes are hit. The biggest difference is the added brake light. Originally I used a larger bulb in the socket but it was too bright (figure 5.2). Putting a smaller bulb (like that used in the old running light socket) was perfect.
I will feel much more comfortable cruising around at night in my 300SD now knowing that people behind me will actually know I am there now, and know when I am braking. The addition of a center brake lamp will also compliment the enhanced visibility of this project, that is certainly on the list for me. I hope you guys find this useful!
Figures:
1.1, 1.2: The LED lamp that I used. Typical truck lamp.
Figure 3.1, 3.2: The aftermath of a lot of cutting/trimming
Figure 3.3: proof of concept hooked up to car battery
Figure 4.1: wired and ready for assembly
Figure 5.1 brakes on:
5.2: with the "euro" bulb that was too bright
- Using the ENTIRE tail light area as running lights, therefore increased visibility--meaning running lights are angled towards other drivers and not just the ground as stock is set up
- brighter and truer red color
- much quicker response time compared to normal bulbs
- using the typically blank euro fog lights for additional brake lights - increased visibility
- LEDs last much longer and usually do not have to be replaced as long as they are not subject to varying current
- Its really easy
Disclaimer: I am not responsible for any harm or damage as a result of your following these directions. I am not implying or expressing that these taillights may be street legal in your local area.
Ok, so here is what you need:
- figures 1.1, 1.2: a DOT-approved 3 prong LED taillamp from NAPA, the type that you see on trailers and trucks. Cost about $25 if I remember correctly. Mine was about 3.5" diameter, filling up the whole red area of the tail light
- w126 tail lamp assembly
- soldering iron plus flux, shrink wrap, solder, and bullet-type electrical pins
- some way to cut plastic. Doesn't need to be pretty. I used a dremel with a variety of tips
- super glue
- about 1-2 hours of time
1. Completely disassemble the tail lamp. You'll have to separate the gasket (good time to replace it too), lens assembly, "reflector" assembly, and the metal strip with light sockets.
2. cut out room for the LED lamp in the reflector assembly. This takes some time and patience to get perfectly right. I got it after about an hour of trimming. You have to make sure to take the middle light separator out. Interesting note is that the plastic is crudely painted "reflective" silver. I can't imagine it doing much good in terms of light reflectivity.
3. Eventually get the LED snug in the reflector assembly so that it presses up against the lens/refractors (figures 3.1, 3.2). A couple dabs of super glue to the reflector assembly will make sure it doesn't go anywhere. Secure the screws to the lens, making it all one piece again. A good idea to test out the LED on a car battery for proof of concept (figure 3.3)
4. Wiring! Everybody's favorite thing! Actually it couldn't get ANY easier than this. First off, take either the bulb socket for the running lamp or the taillight and snip the wire off of it. Put that bulb socket in the "blank" space, where the euro fog light would go. The LED bulb I had already had the appropriate connections molded into the plastic: "tail", "ground" and "brake".
Connect and solder:After that is all neatly done you can connect everything back up (figure 4.1)
- black and red wire to the "brake" connector. Solder this to a bullet type connector and plug in. Solder in another wire to the bullet connector (so it will have two coming off of it) and solder the other end to the socket you just popped in the euro fog spot. Having these two in series will trick the car into thinking there is no bulb out (LED resistance is negligible in comparison) and they will light in unison.
- Connect the Green/white wire to the "tail" plug via another bullet-type connector
- Solder the ground wire/bullet anywhere on the metal strip holding the bulb sockets. The whole thing is a ground.
5. Plug it in and try it out! (Figure 5.1) See the difference--I apologize my camera is NOT good at taking night shots so it is difficult to see. The camera actually makes it look a bit worse than stock but I can guarantee you in person the difference is dramatic. Remember that LEDs produce one wavelength of light and bulbs produce a spectrum, I think that whatever the wavelength is for these LEDs is not well reproduced by my cheap camera whereas the spectrum is sort of a "flood" of light. Anyways, I noticed the normal taillights are not only pointing down and using 1/4 or so of the available space, but they are also amber colored. Using the LEDs brought light to the entire surface including the part FACING drivers behind you, and they light brighter as the brakes are hit. The biggest difference is the added brake light. Originally I used a larger bulb in the socket but it was too bright (figure 5.2). Putting a smaller bulb (like that used in the old running light socket) was perfect.
I will feel much more comfortable cruising around at night in my 300SD now knowing that people behind me will actually know I am there now, and know when I am braking. The addition of a center brake lamp will also compliment the enhanced visibility of this project, that is certainly on the list for me. I hope you guys find this useful!
Figures:
1.1, 1.2: The LED lamp that I used. Typical truck lamp.
Figure 3.1, 3.2: The aftermath of a lot of cutting/trimming
Figure 3.3: proof of concept hooked up to car battery
Figure 4.1: wired and ready for assembly
Figure 5.1 brakes on:
5.2: with the "euro" bulb that was too bright
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