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M-Series Military Vehicle Headlight Conversion

Mike Sommer provided this write up on converting the headlights in his M-37 to 12 volts. The description will work, with few or no modifications, on most American M-series military vehicles.


I have had a few people ask me lately about my 12v headlights in my M-37 and they were surprised enough at my simple M-series setup so I thought I'd pass it on.

Why is this a good idea? Very simple: 24v headlights=$25 per side, 12v headlights=$4 per side, right?

Getting started:

The conversion starts with an aircraft 24v solenoid (must be double throw type). This should cost you about $30. Mount it in a convenient spot under the hood (left fenderwell works well on the M-37). Run a 12v line from your batteries to this solenoid. Disconnect the line that feeds the 24v hi-lo switch and bring it up to the solenoid location as well.

The hook up:

Connect the hi-low switch feed line to the first pole on the solenoid, ground the second pole, attach the 12v line to the third pole, and take the output back to the hilo switch. Use the cheap autoparts crimp-on Douglas connectors when fabricating, of course. Now you have 12v to the hi-lo switch (and from there to the headlights) instead of 24v.

Adapt the headlights:

Go to a junkyard or to the help section of your autoparts store, get two civilian headlight pigtails, crimp Douglas connectors on the pigtails, and now you have adapters so you don't have to damage your MV wiring. Plug in your 12v headlights and check to see if you have the pigtails plugged in right, and Voila! No kidding, I had this hooked up and working in 15 minutes. No more $25 bulbs for me !!

All done:

Easy to change back too, for when you want the authentic military 24v headlights.

Oh yeah, for $8 per side your old MV can have halogens!!

If you are concerned about mismatched battery usage, then rotate the batteries once in a while.

PS, this also gives you a 12v source in the engine compartment for standard timing lights, Etc.

By the way, a variation on this would work for those of you who insist (for some peculiar reason) to go all 12v on your MV. Make the main lightswitch feed a 12v feed and switch every bulb in the truck and you have an instant 12v lighting system. I recommend 12v headlights and 24v everything else.

Questions? E-mail me at Amikesomm@aol.com

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