I recently changed out my original starter relay for a generic unit and thought at the time that I would like to do the headlight relay as well. Also, from the time I first saw the S57 diagram I didnt like the idea of headlight current flowing through the rotary dash switch, so this was an opportunity to to change that as well.

I had some standard 40A 12V relays on hand as I bought a cheaper by the half dozen batch for another project , and the headlight relay can be changed out to a unit which is a standard VW headlight relay and also a sunroof control relay on many US cars. The same functionality has quite a few ID/part numbers, these include DNI0127, LR35, BWD R3018, JD142C-12V and VWC-111-941-583

First step is to take the 12V switch wire (blue) off the old headlight relay and use that to trigger the 40A relay. Power comes from the firewall bulkhead terminal point on that side via a heavier than standard gauge wire, with the idea that a more direct chunky wiring will drop less voltage on its way to the headlights. Some people may like to fuse this line, I didnt, but whatever you do please use fully insulated spade terminals wherever you are replacing or creating connections. Output of the load relay is just a short loop to the new headlight relay done in the same heavier gauge. The headlight switch is now only operating a relay not passing headlight current.

All you need to do is transfer the spade connectors to the functional equivalent terminals on the new headlight relay (diagram on case, look at function not numbers). After the power from the load relay there are only four more connectors, two for the relay coil and one each high beam and low beam. You need to be careful with the coil termination as the second 12V (brown) needs to go on the correct coil terminal (polarity matters in this case). If you get this wrong and flash the headlights it will try and light high beam through the relay coil and non Lucas self inflicted smoke may happen.

The only issue I found with the relay was the lack of a mounting tab or even a slot to push it onto a tab on the car. It only had a small spring clip on it which was useless for my situation. I made up a tab and used some high temperature epoxy to secure it to the relay. After that it was just a matter of wrapping things up to make it as beautiful as possible. It made me fell better fixing the switch thing and the low beams look stronger now.

An added bonus came with this little upgrade. My hazard lights have never worked, got an occasional flash but pretty much dead for a year or so. Was looking at digging into that when a new horn pad arrives from David Boger. While testing the lights and reaching through the wheel to operate the switch I apparently brushed the switch and turned the hazards on. I didnt notice as they didnt work. Later that night I went out in the dark and notice a pulsing light under the garage rolladoor. Go have a look and there is the car happily sitting there with the hazard lights flashing. Turn them off, turn on, off , on , off, on, now they work perfectly. I will try and remember to use them occasionally to give them some exercise.

Any AU/NZ people wanting an original starter or headlight relay, feel free to contact me. You can have them for nothing , just pay pack/post.

Picture at start





I would like to say this is where I paused for a work in progress shot, but really this is where I said "oh crap, I havent got the right connectors" and work stopped for the day. Used the original mounting holes for the new relays.





End result





Relay case diagram




Circuit diagram (use at your own peril)

 

Good work!

Does that DNI027 relay have the 'latching' capability?

Cheers
DD

 

Yes it does, pulse once it changes over, pulse again it changes back. I think the little cross bar on the switch in the relay case diagram is supposed to indicate that its latching and the other switch isnt.

 

Just thought I would finish this off with some real world results. The job is 5 months old but hadnt driven the car at night. Had the opportunity last night and the result is great. The low beam is now a nice white light, instead of the insipid yellow glow I enjoyed before.

This is great for me as I am in wombat country, and you dont want to hit one of those compact though heavy little suckers. They are about 30% of the local panel shops business.