Dear Viard
I have an idea of the functionality of that third screwed terminals relay (5 terminals).
Of course as your harness is old and time erases everything, your color description of each cable is not accurate.
This is what you indicated, and here after what I think it should be:
Terminal 85 (control pin) = Brown (ground all the time). Correct
Terminal 86 (control pin) = Yellow / grey. NO suggestion on this
Terminal 30/51 (feed) =. White/violet. NO, it should be WHITE / YELLOW, and is the Headlight feed wire
Terminal 87 (output position 1) = Yellow (correct). This is the LOW BEAM output for headlights
Terminal 87a (output position 2) = White (correct). This is the HIGH BEAM output for headlights
So my opinion after thinking the issue some time, is that this is a kind of two position output relay for the headlights or something related to them.
Normally the HIGH BEAM/LOW BEAM headlight switching is made by the muli-function steering wheel switch assembly on W113. On W111 that is done via a foot operated switch if your car is prior to 1967.
It may be the case that you have an originally installed accessory that uses the headlight signal for some purpose.
The first thing to do to confirm my hypothesis, will be to check if cable attached to terminal 30 is hot when you turn on the headlights via the main light switch at the dashboard.
Then if that is true go forward to look what is not connected near headlights at front of the car.
Remember that on a standard W113, each headlight is fed through the main fuse box on circuits 9/10 and 11/12.
Best regards
Eng. Leonardo Peterssen
Www.wiredoktor.com
Visit my website
Dear friends / Viard
Illumination came to my mind, i know now what that strange relay should be doing….
Let’ s start from the beginning as any Sherlock Holmes investigation….
1. It is a 5 Prong relay.
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So its intended purpose is to select between two posible answers. One answer will go through port 87, and the other for port 87A
2. It is a permute relay
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Which means that at each terminal 86 activation it will switch and stay in that position either 87 or 87A
3. It has screwed in terminals , not plug in as regular Mercedes relays used on W113
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So this is an aftermarket addition
4. Cable colors
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Viard said that terminal 30 (input side of the relay for the switching load) was WHITE/VIOLET, and I thought it was incorrect and should be WHITE/YELLOW. Definitely Viard was RIGHT.
WHITE/VIOLET is the color that normally Mercedes uses for the HIGH BEAM HORN, which was forbidden on US sold cars, but was of common use on European cars. This LIGHT HORN was activated by pulling the steering multiswitch toward the driver, with the car running or at IGNITION OFF position.
So, VIARD said that port 86 (trigger positive signal) was fed with a gray/yellow wire. And that port 85 was connected to a BROWN wire which means constant ground.
And output wires 87 to YELLOW which is the colour used for LOW BEAM, AND FINALLY WHITE to 87A which is the colour used for HIGH BEAM.
THE CONCLUSION is that this strange relay what does is to switch the LIGHT HORN (white/violet) toward the LOW BEAM circuit (YELLOW) or the HIGH BEAM circuit, every time the GRAY/YELLOW (86) Wire is triggered.
So confirm that this is so by looking at the route that have the WHITE and YELLOW cables. They should go to the MAIN FUSE BOX input side on port 9 and 11.
Have all a nice day.
Happy to have solved this mystery.
Best regards
Eng. Leonardo Peterssen
www.wiredoktor.comVisit my site