M-38 Electrical

Biff · Post by **Biff** » Wed Jan 15, 2020 10:32 am

Is there a reason I can’t use the original 24 volt M-38 light switch when doing a 12 volt conversion? Isn’t a switch just a switch regardless of voltage?

Eades · Post by **Eades** » Wed Jan 15, 2020 10:50 am

The switch will not care what voltage you are sending through it. It will still work. My M715 is running 12 volt through it and not an issue.

Post by **wesk** » Wed Jan 15, 2020 1:19 pm

Just keep in mind if you are using any military light switch manufactured after the two old Scintiila switches in 1951 then the switch is rated at 24 volts and that rating includes the internal CB. The switch contacts will handle the switch to 12V but the rating in amps of the circuit breaker will not be correct for 12V lamps. So I would suggest you install fuses or CB's specific to tghe wattage/amp draw of your 12V lamps and flasher.

mdainsd · Post by **mdainsd** » Wed Jan 15, 2020 3:56 pm

Also, the panel light dim function wont work on 12V, no big deal, leave them on high.

Post by **wesk** » Wed Jan 15, 2020 7:25 pm

Good point. One could open the switch up and change the variable resistor with one in the correct range for a 12V system but just about all the switches built after 52 are the throw away type and used a crimped band around the edge instead of screws between the halves like the old switches. Probably quicker to add a separate rheostat for the 12V dash lamps. There are many of the old style switches still on the market and they are completely rebuildable and easy to dis-assemble and re-assemble.

Check out my album M Series Lighting: http://www.willysmjeeps.com/v2/modules. ... _album.php

Either one of the first two switches can be easily modified.

RonD2 · Post by **RonD2** » Wed Jan 15, 2020 9:05 pm

Yes, the old style (triangular face) switches are easily disassembled for rebuild, however you'll likely need to have more than a few on hand to scavenge internal parts from. It doesn't mean there's no parts out there, but I've never seen any NOS internal parts available anywhere. Take a look for yourself. I'd be interested if you find more than you need.

For example, the main switch rotor is made of plastic and is busted on 6 of the 7 switches I have. In my spare time I'm researching to have some made out of Delrin if I can keep the cost reasonable. It's all they need to work again.

The only vendor I've seen who advertises some of the NOS old-style triangular face switches lists them for $145 a pop the last time I looked.

Beware of those modern hi-tech push-buttton switches. Many reports they're junk (besides the $350 price tag). Apparently only our Uncle Sam can afford them.

mdainsd · Post by **mdainsd** » Wed Jan 15, 2020 10:06 pm

The triangle ones offer a few surprises. NOS ones often do not work. The silver contacts inside are tarnished black. That requires a careful surgery. If you ever do one, do it on a surface that will capture all the little bits and pieces that are going to fall out.

Also a big problem with those is the unsuspecting owner takes off the three levers to install it. Then goes to put the levers back on. The "lock" lever shaft will push in while pushing on the lever. An internal spring instantly pops out of place and jams up the lock lever once the lever screw is tightened.

Pro Tip: NEVER take the "lock" lever off of the early switch unless you have the switch opened up on the bench. With just the other two levers off you can install the switch into the dash.

Post by **wesk** » Wed Jan 15, 2020 11:38 pm

I cannot agree that the old Scintillas are any better or worse then their replacements since 1952. I can say the 40 or so I have worked with over the last 50 years have treated me quite well. It does help to use the free service manual here on our web site's download pages. The reason I have stayed with these old style Bendix switches is because they are built much sturdier than any of the replacements out there since 1952 and their internals are easily accessible for both repair and modification. There are far worse electrical switches out there that can ruin your day!

4x4M38 · Post by **4x4M38** » Thu Jan 16, 2020 6:38 am

I believe Brent Nullins has some of the two plug switches for sale for less than 145.00.

mdainsd · Post by **mdainsd** » Thu Jan 16, 2020 7:57 am

Wes. I use the old Scintilla's as they are the correct switch for the vehicles in the stable. I actually quite like them. The build quality is great, a standard from a time long past. I was offering some things to look out for when servicing them.