Modern Headlight Switch Reverse Engineering help

[topherchrisb]

Hey everyone... I'm having trouble trying to figure out how a modern ford focus headlight switch works. I'm wanting a more modern look and function in my car and as part of that I've grown to love the size and functionality with the switch in the link below. The unit fits perfectly just left of the steering column and is completely visible through the steering wheel with the RT turn signal unit. Here is a post (https://thefactoryfiveforum.com/showthread.php?41821-topherchrisb-s-project-quot-Mako-quot-IRS-MK4-Coyote-10255&p=517810&viewfull=1#post517810) in my build thread with how it mocks up from driver's point of view.

https://partshawk.com/ford-focus-headlight-switch-standard-motor-products-hls-1582.html

There are 6 pins on the switch. When I first started this venture I thought this was going to be easy...
1 pin 12v+
1 pin trunk button
1 pin fog light button (would use for interior lights likely)
1 pin running light
1 pin head light
1 pin ambient light sensor

I took the switch apart and immediately saw one of the pins is a ground as it's trace goes around the circuit board and having continuity with so many other places. I also found a second pin that had a trace that's not quite as big as the identified ground but much larger than the others so I'm thinking that's 12v+. Next I tried testing continuity between all the pins while pressing the trunk button and wasn't successful. What the heck is going on!? Then looking at a few things online I see mentions of CAN bus control units. OMG... I never knew such a thing existed. I've been trying to find something online that helps me determine how this switch functions and if it is a CAN bus device but haven't had any luck.

Do any of you electrical gurus have any guidance or pointers to online material that can help me figure this out? At this point I'm curious just to know how it works even if I can't use it in my setup. I hate not being able to understand how something works. I can post some pictures of the board if anyone thinks that'll be helpful.

[F500guy]

I can tell it probably is a computer input sink/source type. There is a write up at the Miata site about re-purposing switches. It has some drawings, they would not be specific to your plan but maybe explain how it work. Not sure if that would help you out. https://forum.miata.net/vb/showthread.php?t=764054

[Fordman114]

I wouldn’t doubt that that circuitry runs through the body control module in order to work.

[rich grsc]

Just google search it. A bunch of results. :rolleyes:

[maclonchas]

You might look at the wiring diagram for this switch:

Here is a link to look at the hookups:

https://portal-diagnostov.com/en/2020/04/11/headlights-ford-focus-svt-2002-system-wiring-diagrams/

Bill

[edwardb]

Nice idea, but not likely very practical. You mention in your build thread that electrical isn't your strength and this is more like a master's class. :o

This URL shows the schematic for a 2012 Focus (the vintage of the switch you cite) headlight circuit: https://portal-diagnostov.com/en/2020/04/11/headlights-ford-focus-sel-2012-system-wiring-diagrams/. As suspected, that switch is an input device to the body control module. Pretty standard stuff for most modern cars. Further evidenced by none of what you found inside the switch has capacity to directly switch anything with any current to speak of. That good old AC-Delco switch isn't that bad. Really...

[rich grsc]

Nice idea, but not likely very practical. You mention in your build thread that electrical isn't your strength and this is more like a master's class. :o

This URL shows the schematic for a 2012 Focus (the vintage of the switch you cite) headlight circuit: https://portal-diagnostov.com/en/2020/04/11/headlights-ford-focus-sel-2012-system-wiring-diagrams/. As suspected, that switch is an input device to the body control module. Pretty standard stuff for most modern cars. Further evidenced by none of what you found inside the switch has capacity to directly switch anything with any current to speak of. That good old AC-Delco switch isn't that bad. Really...
Now wait, I have and old Apple computer from the 90's, surely something could be rigged up? Add in a couple relays. :eek:

[steno]

That switch could be used to trigger multiple power relays. But it’s a bit of work. My SBF roadster has 3 relays… I wish I didn’t need them. I love the K.I.S.S. method!!

[Jeff Kleiner]

Put 12 volts in, connect the headlights to the outgoing pole then turn it on and watch for the smoke signals ;)

Jeff

[steno]

Put 12 volts in, connect the headlights to the outgoing pole then turn it on and watch for the smoke signals ;)

Jeff
You’re EVIL!!

[Windsor]

Put 12 volts in, connect the headlights to the outgoing pole then turn it on and watch for the smoke signals ;)

Jeff

If it's designed for CANBUS 3.3/5v, you may not even need to wait for "turn it on" before the magic smoke starts flowing, just add that 12v juice by connecting the battery.

[MB750]

Yup, that switch block is CANbus. Sorry. Unless you have experience converting CANbus into digital I/O it's not gonna work in your project.

[topherchrisb]

I'm not afraid to cause a little smoke in the pursuit of knowledge. I do have a raspberry pi, arduino and particle boards in my hobby closet and am a capable programmer. Some of the comments here have evolved my searching and it seems I'm seeing more relevant info now. I even see some arduino CAN controllers are commonly available. I realize this topic probably isn't best suited here so once I find a more targeted forum I'll start the conversation there. If I get any useful progress with the project I'll update the topic and post my findings in this thread. At my pace I wouldn't expect anything for a couple months. :P