New Project: Push Button M-Series Light Switch

[corax]

Pin A: Stop Lamp Switch. Runs through brake light switch to Pin K.
Pin K: Stop Lamp Switch. Runs from pin A through brake light switch.
Pin C: Stop Lights. Hot when brakes applied. Runs to turn signal switch if used.

In my experience the brake light switch makes contact (closed circuit / continuity) when you step on the pedal, allowing current to flow to the lights and turn them on. I would guess that A and K just get tied together (continuity, as if the pedal was being stepped on to allow current to flow) that being said, you should probably stick a 7.5 or 5 amp fuse on that wire just to make sure nothing gets too hot when you test it.

Just a guess, but the circuit (from positive to "load" or ground) goes from A to the nonexistant brake switch (or wires tied together) back to K and then comes out of the switch again on pin C (+ voltage to brake lights) which doesn't make sense to me because if they want the ability to kill the lights it could just go from A to the switch to the lights and they could kill it before it even leaves your fancy switch.

I'd really need to see what the switch's internal circuit diagram looks like to say anything for sure (or spend some quality time with an ohm-meter). If you can find a link to the Humvee wiring diagram, that might help - it would also tell me it the switch controls everything on the ground side or by supplying voltage (big diff)

One other oddity, from the pinout you posted, where does it get power from?

[slosurfer]

I think I'm following what you're saying Keith. I'll find some more diagrams and info tonight.

Also, I believe the switch gets its power from pin F Battery Power Lead. The switch itself has the ground wire.

[slosurfer]

Okay, I think I figured it out. HEre's a list of the "circuits"
http://www.olive-drab.com/od_mseries_circuits.php3

Just look up the circuit for each pin. So we're looking at 22 and 75 circuits. After rereading it, I can just use pin C since pin A and K go to the stop switch which is actually for your turn signals. So I can just leave A and K alone for right now.

[slosurfer]

Okay here's a wiring diagram. I'll try to snag it and post it but here's the link:
http://m37.crwdesigns.com/m37wiring.jpg

Look at the Light Control Switch near the center of the diagram.
So it looks like A and K just loop with a stop switch to make/break continuity, and then C goes to Turn Signal Relay. Not sure what those symbols on A and K are, are they fuses?

Edit: I looked at the legend and those are just single wire connectors.

So I'm guessing I need to loop A and K and run C to whatever relay I chose to run with that switch, correct?

[corax]

Look at the Light Control Switch near the center of the diagram.
So it looks like A and K just loop with a stop switch to make/break continuity, and then C goes to Turn Signal Relay.
So I'm guessing I need to loop A and K and run C to whatever relay I chose to run with that switch, correct?

Yep, that's what I was thinking.

Also, looking at the wiring diagram, it would appear the switch does control everything on the positive side (turns things on by supplying voltage, not by giving a ground). So relay wiring should be pretty simple - wire from your switch to the relay coil / other side of relay coil to ground.

[slosurfer]

Look at the Light Control Switch near the center of the diagram.
So it looks like A and K just loop with a stop switch to make/break continuity, and then C goes to Turn Signal Relay.
So I'm guessing I need to loop A and K and run C to whatever relay I chose to run with that switch, correct?

Yep, that's what I was thinking.

Also, looking at the wiring diagram, it would appear the switch does control everything on the positive side (turns things on by supplying voltage, not by giving a ground). So relay wiring should be pretty simple - wire from your switch to the relay coil / other side of relay coil to ground.

Thanks Keith!

[Rock Slide]

Chris, any updates on this? Curious to see how it turned out.

[slosurfer]

Sorry, no updates, I put it on hold for a bit because I thought I was getting a roll cage. I needed to make sure it would fit with the roll cage bar coming down right there.

Funds got short, so no roll cage for awhile, so I'll get on this pretty soon. I'll just have to keep it as far inboard as I can to leave room for a roll cage down the road.

[Crinale]

Can always run the rollcage into the dash, iv seen other trucks do it this way... follow the A pillar all the way into the dash. That way the bar will be behind the switch, and no risk of hitting your knees on the bar gettin into the truck ^_^

[slosurfer]

Yeah, there's always that way. I actually had my eye on one that was already built.