M37 Ignition Switch

[MatthewH]

I reciently took in a fellow SS'ers M37 project to help out with some sheetmetal/body work, and along with some other minor issues, we're in the process of installing a new igniton switch. We suspect the old one is the culprit, but the one currently in the truck isn't original, and I'm not positive it's wired correctly.

The new one has 4 ports, but I only see 3 wires wired into the old switch. My question is which ones go where, using the metal tags on the original wires. The new switch has each port labeled, A,B,C,D, but the wiring diagrams don't show the back of the switch.

Pic 1 is the tab up on the front of the switch, pic 2 is the orientation of the ports with the tab up

Any/all info would be a great help.

Thanks
MatthewH

 

[Capt.Marion]

I think it should be rather simple. The master power switch on the M37 is simply a binary switch. Either everything's on, or everything's off. If you have a continuity checker/multimeter, you could probably figure it out.

I'd look at my M37 for you, but it's currently 1100 miles away. Hopefully someone else will chime in, too.

 

[319]

Found this:

http://www.steelsoldiers.com/electrical/80021-replacing-keyed-switch-m37.html


"Circuit 11 is your incoming (always) hot wire coming from your circuit breakers; goes to switch pin A. Later, M37B1 schematics show this also jumpered to switch pin C; early schematics show nothing connected to pin C.
Circuit 12 is outgoing to your coil; goes to switch pin D.
Circuit 27 is outgoing to your dash spider harness (powers your gauges); goes to switch pin B."

 

[maxim]

Might help

 

[135gmc]

If the new switch has four terminals, there is a chance that is really has two switched circuits insteal of one circuit with three output terminals. I have switches like this in some of my equipment. Check it out with an ohm meter before you install it-

 

[MatthewH]

Hey, thanks everybody. While I did find a few wiring schematics, I didn't find that one in the manuals that came with the truck, will look further and see if I infact have it.

I'll get it wired in this weekend and see if it helps in the drain on the batteries we're having.

Thanks again

 

[WarrenD]

You can also do what I did (though not authentic) and install a keyed electrical disconnect switch. I hooked mine to the neg cable before it got back to the battery. Key out, no power, period! Keeps kids of all ages from burning out my points if I'm not right with the vehicle at shows.

 

[MatthewH]

You can also do what I did (though not authentic) and install a keyed electrical disconnect switch. I hooked mine to the neg cable before it got back to the battery. Key out, no power, period! Keeps kids of all ages from burning out my points if I'm not right with the vehicle at shows.

Its going to get a master disconnect switch right by the battery, similar to what I've seen on other military trucks.

I probed the new switch, and found with the switch off, nothing had continuity, but when I turned the switch to on, I had continuity between port A and port B, and port C and port D, but thats it. I'll have to go look for the 4th jumper wire, and make sure this switch is correct to the truck.