I am planning on installing a third brake light in my W108. I purchased a used BMW E30 unit.

Problem I have is that I need some sort of mounting pedestal for the third brake light.

Any ideas on what i should use?

I am thinking of using a polycarbonate or ABS plastic electrical box.

Somwthing like this.

WP-24F Polycarbonate Electronic Enclosure with NEMA Rating

I like this box because it has a flange that can secure it to the rear parcel shelf with screws. Power wire would be run off one of the rear brake lights from the trunk through the underside of the parcel shelf. This way all wiring is concealed.

I have spare MB Tex cognac material that I plan to use to cover the pedestal and the beige part of the light unit.

This is what the E30 third brake light looks like in the W108. I wedged it in to show the pedestal height needed.

The home center gray outdoor electrical boxes would be fine.

Before making mounts, I'd wedge and wire it up then look from the rear of the car to make sure the light can be seen by higher vehicles. Lights work two ways. One is where the lens glows and the other is where light is projected to the viewer.
A glowing lens can be seen off angle but a projected beam can't.

A perfect example of poor light design is the latest clear cover over headlights / front turn signals. While these lights pass brightness ( light projected ) they are poor in off angle situations where a glowing lens would be helpful. And these off angle situations become critical when a car is 90* to the viewer and making a left turn across the viewer.

With the window-slant, it might be difficult getting a drill in there from above, and if I recall, the rear shelf is double-wall, so drilling from below might not be possible. I'd consider velcro to the shelf-carpet.
Whatever attachment you wind up with, you need to allow for getting the light out or apart for bulb replacement.

Happy Motoring, Mark

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DrDKW

All of the incandescent-type third-brake lights I've seen have ribbed lenses to allow visibility at off-angles. But now, you have me curious about the angle-visibility of the multi-led brake-light on my '98 Nissan Altima's trunk-spoiler.
I replaced the original headlights on my Altima with the clear cover style used on the '00-'01. I prefer the more expensive look of the later style, and my originals were so fogged, the car was undriveable at night! Fortunately, on these Altimas, there are side-markers, and the front parking/turn signals wrap around the side to compensate for any lack of side-visibility from the headlights.

Happy Motoring, Mark

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DrDKW

Thank you to both of you for your comments.

The lens is ribbed on the inside so I am assuming there will be a wide viewing angle.

The beige part of the housing lifts up at a 45 degree angle. There are two tabs that keep the bulb holder in place. So bulb access is going to be pretty simple. I have also purchased an LED bulb. So hopefully once the third brake light is installed I will never have to change the bulb.

Mark, when you say a double wall what do you mean. Can I get access to the underside of the shelf by removing the rear seat?

Thanks.

On my '72 W114 250 sedan and '82 W123 240D, the steel rear shelf that the carpeted panel sits on has a second steel panel an inch or so below it.
Now my Ponton 180 and Fintail 220S don't have this second panel, so I may be wrong about the W108. However they all have a steel firewall between the back seat and trunk, so there's no access to the rear shelf that way.
You'll need to drill from inside the trunk.

Happy Motoring, Mark

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DrDKW

Understood, thank you Mark.

Okay guys I had the brake light and electrical box covered with some spare cognac vinyl that I had.







I like the way the light fixture turned out. I am not too happy with the shape of the pedestal. It seems a little too square. Unfortunately this was the only size that would fit the light and raise the lens so it can be seen above that vinyl trim piece on the bottom edge of the rear window.

I have another idea in my head. That is to use a chrome Hella/Bosch old style exterior fog light as a third brake light. This would also be mounted on the rear parcel shelf.

This is the type I am thinking of.



What do you guys think would best suit the interior. Would the second option be too much chrome?

I like that Hella light, maybe even use one on each side?
But I wonder that if the lens is not flush against the lens will it cause a reflection, especially at night?

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Csaba
1972 280SEL 4.5, silver

It probably will have some reflection.

I decided to go with this Hella light.





I will see if I can get a LED bulb that has a narrow beam spread. That might help with the reflection.

good job wrapping the housing. looks factory! I was thinking about putting a third brake light for safety purposes as well.

check out this alternative. it's strictly for safety purposes only. Aesthetically it doesn't look bad. but it doesn't look great. If anything it keeps your car looking as stock as possible
It puts the 3rd brake light in the license plate frame. as well as lights the licence plate. its easy. it's reversible and it shouldnt require too much modding.


http://www.amazon.com/Custom-Accessories-92595-Lighted-License/dp/B007LICGLK/ref=sr_1_2?ie=UTF8&qid=1455929758&sr=8-2&keywords=third+brake+light+licence+plate

Thanks.

Reducing the chance of getting rear ended in my 108 is my primary goal. I am seeing too many people of all ages looking down at their smart phones while driving.

I like the concept of the integrated light in the plate frame but it may be too low. Studies have shown, the higher the light the more chance of it being noticed. If anything I would add that in addition to the parcel shelf third light.

I have already changed out the rear tail/brake bulbs to LED. You might want to do that if you have not already. I used LED bulbs that were rated with higher lumens for the brake lights than stock. The brake lights can easily be seen on sunny days.

[QUOTE=
I have already changed out the rear tail/brake bulbs to LED. You might want to do that if you have not already. I used LED bulbs that were rated with higher lumens for the brake lights than stock. The brake lights can easily be seen on sunny days.[/QUOTE]


I did buy some super bright LED bulbs. They are canbus error free but it coulndt outsmart my w124 300d. so i'll use the on my w108. did you happen to replace your blinkers too? and if so, do they flash too fast with LED?

I did change the rear blinkers to LED and yes they do flash to fast. I am going to change them back to incandescent.

The place where I have been buying the LED bulbs sell these load resistor kits to eliminate fast blinker flashing. FYI, I have not tried them.

https://www.superbrightleds.com/cat/flashers-load-resistors/

I agree with mounting it high. IDK if the parcel shelf is high enough. I'd find a way to do a classy mod of the rear dome light so that you have it mounted there, flush to the top of the rear window.

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Current:
2021 Charger Scat Pack Widebody "Sinabee"
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1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k