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Headlight Relays for the W463

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AlanMcR
Posts: 3899

Headlight Relays for the W463

Post#1 » Thu Mar 05, 2015 10:04 am

Problem solved: Intermittent high beam headlights (both)
Side benefit: brighter headlights.

From around 1996 to 2000 the W463 came with a turn signal switch borrowed from the E-class, which had computer module driven lights. The tiny internal contacts which were meant to send a logic signal to the module (on the original car) were re-purposed to switch 120W to the high beams.

Needless to say, they don't last long. One night you will be rocketing down a twisty road and when you switch to the high beams all you will get is inky darkness. Not only that, but the low beam contacts will burn out not long after that.

The solution is to add headlight relays, just like the factory should have. The attached PDF shows the wiring diagram and parts required to install the relays into the factory relay rack under the glove compartment.

I have found that even a "burned out" high beam switch will correctly trigger the relays. So, if your switch has failed you might want to install relays first.

Here is a very dusty picture of the actual install. Most of the wire terminations can't be seen, sorry.
HeadLightRelayPic.jpg
Attachments
HeadlightRelayCircuit.pdf
(31.64 KiB) Downloaded 93 times

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G500Pur
Posts: 801

Re: Headlight Relays for the W463

Post#2 » Mon Apr 06, 2015 2:40 pm

These are SPST relays? Do the Bosch ones you used plug into a blank under your glovebox? Looks like a clean, factory style, mount (except for all that dust in there).

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AlanMcR
Posts: 3899

Re: Headlight Relays for the W463

Post#3 » Mon Apr 06, 2015 3:01 pm

Yes, simple 12V SPST relays. It is the sockets (listed in the PDF) that click into the frame. The relays just plug into the socket.
It came pre-loaded with dust from the Sahara. I've been layering the local desert dust on top. :D

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G500Pur
Posts: 801

Re: Headlight Relays for the W463

Post#4 » Mon Apr 06, 2015 6:35 pm

AlanMcR wrote:It came pre-loaded with dust from the Sahara. I've been layering the local desert dust on top. :D


Now that's a pedigree.

I've got the pdf printed out now, so I get it.

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Otiswesty
Posts: 3218

Re: Headlight Relays for the W463

Post#5 » Wed Jan 11, 2017 8:15 pm

I had this same issue with my G500 a few years ago. The switch is the same as the C class. I replaced my switch using the Cclass part number, much cheaper then using the 463 part number.
Thread here:
http://www.pointedthree.com/disc/forums ... =1#M228484

User avatar
AlanMcR
Posts: 3899

Re: Headlight Relays for the W463

Post#6 » Wed Jan 11, 2017 9:18 pm

Yeah, but the tiny little contacts will just burn out again.
...Alan

Court
Posts: 430

Re: Headlight Relays for the W463

Post#7 » Sun Mar 10, 2019 6:16 pm

Hi Alan,

So given what you have done here is it possible that different relay(s) could be used (5 pin?) to activate DRL in a G thus accomplishing two things?

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AlanMcR
Posts: 3899

Re: Headlight Relays for the W463

Post#8 » Sun Mar 10, 2019 8:10 pm

The easy answer is to install a diode between the stalk and the relay coil for low beam. And then another diode between circuit 15 (ignition on) and the same relay coil. That causes the relay to turn on in either case. The problem comes when you go to hit the high beams. Now both high and low are on.

It looks like one could connect pin 5 of the low beam relay to pin 1 of the high beam relay to solve that. This would rob the low beam relay of power if the high beams are on. Would need some testing, but ought to work. Relay logic is fun!
...Alan

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