Pagoda SL Group

W113 Pagoda SL Group => Electrical and Instruments => Topic started by: 66andBlue on April 21, 2011, 06:43:42

Title: Diodes in 280SL taillight electrical plate ?
Post by: 66andBlue on April 21, 2011, 06:43:42

Here is a question for all you electrical wizards out there.  ;)
The electrical plate (bulb holder) in an early taillight (230SL) has 5 sockets for 5 bulbs: 1. brake light; 2. tail light; 3. parking/clearance light; 4. back-up light; 5. turn signal. And electricity is provided by a 6-pin connector.
The later style plates (on late 280SLs) have only 4 sockets, so one bulb serves two functions, that is, the tail light and clearance light are combined into one, but there is still a 6-pin connector connector. Is my suspicion correct that the two diodes are there to prevent a short between the "tail light" pin and and the "clearance light" pin since both are hot when the headlight switch is turned one notch?

Title: Re: Diodes in 280SL taillight electrical plate ?
Post by: Larry & Norma on April 21, 2011, 08:06:09

Never heard of that but your assumption is correct I think. Without the diodes, for example, when you switched
the side lights on the current would travel back down the unswitched cable and turn your headlights on as they
are wired in parallel with the tail light. Hope this makes sense.
Larry

Title: Re: Diodes in 280SL taillight electrical plate ?
Post by: Richard Madison on April 21, 2011, 09:44:52

Alfred:

Our Tech Manual article on Tail Lights shows an early and a later bulb holder and mentions that there are Diodes in the later version.

The later bulb holder in the Tech article is quite different than the one you show in your message so there seems to have been several versions of bulb holders, more than the two in the Tech article.

Here's the link:

http://www.sl113.org/wiki/Electrical/TailLights

Richard M, NYC

Title: Re: Diodes in 280SL taillight electrical plate ?
Post by: 66andBlue on April 21, 2011, 16:39:22

Hi Richard,
thanks for the link, I am well aware that is there since I added it.  ;) ;D
The photos in my post and the one in the wiki show the same holder, except the back view is not shown in the wiki. I hope I labeled the soldering points correctly!?  Hope that someone will check it again.
Just wanted to see whether the entry can be improved by adding more info on the diodes and what to do when they fail.

Hi Larry, thanks for your explanation.
Is this all there is to these diodes??

Title: Re: Diodes in 280SL taillight electrical plate ?
Post by: Larry & Norma on April 21, 2011, 18:13:23

Is there a circuit diagram with these diodes in?
It is the standard way of driving one light bulb from two sources
without one source affecting the other.
Like the diodes in a car alarm circuit that flashes all indicator lightbulbs
but they still work independently as indicators.
Larry