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1983 Mercedes Benz 300D Turbo Diesel
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69 Posts
Discussion Starter #1
Hey,

I need a working dimmer switch/rheostat for the instrument cluster on my 83 300D. I believe that it was the same from around 77 to 85 or so. The only place I have found that sells them is autohaus, but there is no way I am going to spend $80 for a rheostat!!!

So if you have one laying around or in a parts car that you would like to sell, send me a quick private message with your price and contact info and maybe we can work something out.

Thanks!
 

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1983 Mercedes Benz 300D Turbo Diesel
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69 Posts
Discussion Starter #3
Thanks for the reply, guess I should have been more clear why I want one.

I have for the last few years had my switch jumpered but the light was still frustratingly too dim - like with all W123s. I reciently went to Auto Zone though and for about $15 got a set of two strips that are about maybe 4" long that have a sticky back and 4 superbright LEDs on each and are designed to run off 12V. So I stuck them on the top of the cluster box right in front of the old light prisms and wired them into the cluster boards. WOW, what a HUGE difference!! Not everyone might like the look (and I would have made a slight modification if doing it again, but they are fantastic!!!

So my issue is that while jumpered right now I am getting full brightness which is really bright and so I would like to be able to tone it down a bit. But my original rheostat is trashed and is missing the coil that the slider runs on to give a resistance. But as I said it is not worth $80 to me!:eek:

Thanks!
 

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2003 Volvo V70 5 Speed
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1,784 Posts
any chance of showing us some pictures of your setup?
 

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Registered
1983 Mercedes Benz 300D Turbo Diesel
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69 Posts
Discussion Starter #7
LED Instrument Cluster Lighting Mod DIY

Here is what I did to improve the lighting on my W123's instrument cluster. I have been thrilled with the results and highly recommend it to others as it is not a very obvious change to the original instrument cluster but the effect is HUGE!

As I said before, I went to Auto Zone and picked up a set of two flexible LED light strips each about 4" long that run on 12V. The package had on it "Flex LED" and there was a push button and batteries on the pack so you could see them light up. They came with 3M adhesive backing to make it easy to mount.

So as you can see in the first picture I took the instruments out of the cluster box and drilled two holes about an inch from the center line just big enough for the wires to fit. I fed the wires through as much as I could then stuck the strips using the old prism boxes as a guide to stick them straight.

photo1.jpg

I originally tried just leaving them as they came out of the box, but the light ended up lighting up most of the front seat area too (that is why I was looking for a dimmer switch). However you can see in the first picture that I ended up taking some masking tape and masking out the half of the strips that are closest to the instruments, then painted the other half and exposed wires flat black to blend in. This proved to help tremendously to direct the light to only the cluster and not the rest of the cabin.

photo5.jpg

The next picture shows how to wire them up so that they come on with the old cluster lighting. There are three wires on either side, make sure that you wire the positive of the LED lights (red) to the solder points of the red wires that are already in the cluster circuit board, and the negative of the LED lights (black) is wired to the solder points of the GREY (NOT BLACK) wires that are on the circuit boards.

photo4.jpg

In the next picture, I show how I took my soldering iron and melted indentations in the cluster box for the wires to pass through once the circuit boards are mounted on the cluster box again. I left a fair bit of wire on the LED lights to make life easier when I disassemble the cluster in the future. I just took the excess and twisted it together and tucked it behind the cluster box.

photo2.jpg

Finally here is a picture of the finished result. It looks tremendously better than my crappy phone camera picture shows. There is no glare like in the picture and I love the bright white light the LEDs give off. Before I wouldn't be able to read the trip odometer with the lighting from the prisms, but now I can clearly see everything.

photo3.jpg

Hope someone found this helpful.

Trevor.
 

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Here is what I did to improve the lighting on my W123's instrument cluster. I have been thrilled with the results and highly recommend it to others as it is not a very obvious change to the original instrument cluster but the effect is HUGE!

As I said before, I went to Auto Zone and picked up a set of two flexible LED light strips each about 4" long that run on 12V. The package had on it "Flex LED" and there was a push button and batteries on the pack so you could see them light up. They came with 3M adhesive backing to make it easy to mount.

So as you can see in the first picture I took the instruments out of the cluster box and drilled two holes about an inch from the center line just big enough for the wires to fit. I fed the wires through as much as I could then stuck the strips using the old prism boxes as a guide to stick them straight.

View attachment 347988

I originally tried just leaving them as they came out of the box, but the light ended up lighting up most of the front seat area too (that is why I was looking for a dimmer switch). However you can see in the first picture that I ended up taking some masking tape and masking out the half of the strips that are closest to the instruments, then painted the other half and exposed wires flat black to blend in. This proved to help tremendously to direct the light to only the cluster and not the rest of the cabin.

View attachment 347992

The next picture shows how to wire them up so that they come on with the old cluster lighting. There are three wires on either side, make sure that you wire the positive of the LED lights (red) to the solder points of the red wires that are already in the cluster circuit board, and the negative of the LED lights (black) is wired to the solder points of the GREY (NOT BLACK) wires that are on the circuit boards.

View attachment 347991

In the next picture, I show how I took my soldering iron and melted indentations in the cluster box for the wires to pass through once the circuit boards are mounted on the cluster box again. I left a fair bit of wire on the LED lights to make life easier when I disassemble the cluster in the future. I just took the excess and twisted it together and tucked it behind the cluster box.

View attachment 347989

Finally here is a picture of the finished result. It looks tremendously better than my crappy phone camera picture shows. There is no glare like in the picture and I love the bright white light the LEDs give off. Before I wouldn't be able to read the trip odometer with the lighting from the prisms, but now I can clearly see everything.

View attachment 347990

Hope someone found this helpful.

Trevor.
That is an awesome idea. Did you ever get a dimmer switch to see about dimming the LED's? You can get them on ebay for around 20 to 25 dollars. If not PM me I have an extra laying around I cleaned up.
 
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