Part for Early M38 Light Switch ORD 7729684

RonD2 · Post by **RonD2** » Fri Apr 27, 2018 9:47 pm

I found an early M38 repairable light switch for a song. Opened it up, no corrosion, everything in good shape except the Main Switch Rotor is broken. I'm guessing, but it looks like that Rotor is probably the most common broken part in these switches --- it's made of plastic. I'm hoping my Uncle Sam made a ton of them for stock and enough survived to this day.

It's Item S on Figure 29 in the Manual. So far, I haven't been able to find a part number for it.

Does anybody know if there's any available --- or am I dreaming?

If not, I'm thinking a 3D printer and a block of Delrin.

Thanks!

Post by **wesk** » Sat Apr 28, 2018 12:41 am

I do not think you are going to have a lot of luck finding that rotor.

The 2 plug light switch in your picture, ORD# 7729684 Scintilla PN 10-34880-1 was used in the 1951-52 M37 & the M38 thru MC35387 The M38 version of that light switch is the same ORD # but Scintilla PN 10-34880 or 10-34880-1.

The rotor for the 10-34880-1 is ORD part number 7408096, Bendix-Scintilla PN 10-35236 in the M37's ORD 9.

The rotor for the two plug M38's 10-34880 or 10-34880-1 switch is 10-34884 in the M38's 1950 & 1955ORD 9's.

I didn't find any of these rotors on the market search.

The M38 ORD 9's list all the internal parts for those two early Bendix-Scintilla light switches. The illustration is on page 107 and the parts are listed in section 0607.

mdainsd · Post by **mdainsd** » Sat Apr 28, 2018 1:24 pm

Is there enough of the rotor left to give JB Weld a shot?

Those switches are a little tough to find, not surprised in the absence of parts.

chuck · Post by **chuck** » Sat Apr 28, 2018 3:30 pm

I believe I have at least one for sale. Clean and tested. $95 + shipping.

Post by **wesk** » Sat Apr 28, 2018 11:00 pm

Is that a rotor or a bendix light switch assembly?

chuck · Post by **chuck** » Sun Apr 29, 2018 4:48 am

The entire light switch assy.

wadefreedomvehicles · Post by **wadefreedomvehicles** » Sun Apr 29, 2018 7:55 pm

I bought parts front piece to get one of them for my light switch. Although something else is wrong with my switch cause only the service lights work...
Somebody needs to design the piece in a 3d program and have them printed.

RonD2 · Post by **RonD2** » Sun Apr 29, 2018 9:55 pm

Thanks guys!

I'm going to look into fabrication of the rotor. I know some folks with that capability but it'll take some time to get free answers and advice. I'm quite sure the technology to make them isn't the problem. The problem will be cost and the market demand for them.

No sense making them if they'd have to cost some gold-plated price like the entire switch itself does. I'd probably only pay about $20 tops to get a plastic rotor. Gauging demand won't be easy.

I've become fairly patient in this hobby --- so I'm still hoping somebody has a gross case (of 144) laid up somewhere collecting dust.

I suppose Chuck's $95 offer for the switch is reasonable as I see them go elsewhere for $125 to $150. While I appreciate it, not happening from me. No guarantee the rotor in that switch or any other won't snap next week and I'd be back in the same boat.

If I find out anything hopeful on fabrication I'll update the post.

m3a1 · Post by **m3a1** » Sun Apr 29, 2018 11:29 pm

Or take it to a machine shop and see if they will take on the job of making one. Never hurts to ask...particularly if you have a suitable hunk of material for them to make one from.

Just a thought.

Post by **wesk** » Sun Apr 29, 2018 11:46 pm

Plastic extrusion business may offer more help then a machine shop. The early two plug Bendix switch is not that difficult to find. I have stumbled across them by the boxful cheap. It's the 2nd Bendix one plug switch that is tough to find.

Unless you feel very strongly about the correct switch for your serial number jeep, I would shop for the current issue push button switch. It plugs into the same hole in the dash and uses the same electrical plug. These are showing up current surplus.

Xamon · Post by **Xamon** » Mon Apr 30, 2018 6:59 am

I do some 3d printing and even a bit of modelling, but I need a lot of measurements to do it. I am also in Canada of course but you can take the files to places like shapeways. They can even do laser sintered metal if you want.

RonD2 · Post by **RonD2** » Mon Apr 30, 2018 7:29 am

I'm pretty certain the rotor has to be made out of non-electrically conducting material --- plastic --- because of the 3 spring-loaded contacts mounted on it.

I suggested Delrin earlier as it doesn't conduct electricity, is stronger than plastic, has excellent self-lubricating and machinability properties, and most important -- it's cheap! I don't know whether or not the piece could be cut on a water or laser CNC machine or whether it'd have to be a steel bladed machine to do it.

Yes, have to get it drawn to capture all the dimensions first which is likely the biggest expense along with programming the cutting tool. Hopefully my friends in the business can give me a ballpark figure on the costs involved to make one to 99. New territory!

I paid $27 for my switch. It'd be nice to get it up and running for another $20.

4x4M38 · Post by **4x4M38** » Mon Apr 30, 2018 8:30 am

Brent Mullins is selling new two plug switches on eBay.

RonD2 · Post by **RonD2** » Mon Apr 30, 2018 10:10 am

Yikes!

$495 for the push-button type.

https://www.eriksmilitarysurplus.com/pubuliswmv12.html

4x4M38 · Post by **4x4M38** » Mon Apr 30, 2018 11:37 am

Push button is a very late, non-M38 switch Ron.