'54 M38A1 Starter switch

CharlieC · Post by **CharlieC** » Thu Jul 05, 2018 10:25 pm

Trying to get a '54 M38A1 going that I inherited...

I've burned up two starters before finally figuring out the problem is the starter switch plunger sticking. This has happened on a new switch I wrote off to being poor quality. Happened on another switch where it appeared to short due to the insulating board material being burnt away on the starter contact. It's happening now on an original piece that looks to be in good condition even after I have cleaned the contacts with a Dremel brush wheel. This has been an expensive education putting these experiences together to now understand what has happened past and present. I can say this last attempt where it stuck with the clean electrodes, happened while the batteries were too low to turn the motor over. They are being charged now with a 24v Battery Tender brand charger.

I was able to crank the motor when I first got it 18-24 months ago, but had to tackle fuel system issues to get back to where I am now.

Any ideas/help would be appreciated.

Thanks,
Charlie

Post by **wesk** » Thu Jul 05, 2018 10:56 pm

You are sure those two starters were 24V starters?

The starter switch issue has been addressed on this site a few times. Use the search function just above the forum index:

Forum FAQ Search Usergroups Profile No new messages Log out

Google search "M38A1 starter switch problem mjeeps.com" will also get you all posts as well.

Mike_B · Post by **Mike_B** » Fri Jul 06, 2018 10:26 am

Have you actually tested the starter motor itself? You could have something grounded internally causing the switch contacts to weld together.

Mike B

CharlieC · Post by **CharlieC** » Fri Jul 06, 2018 10:37 am

Wes

Thanks for the reply. I'm confident they are 24v, as the second one that burned was freshly rewound by an old-time electric motor shop.

The first one dying was maybe a bit of a mystery, but I kept the switch and disassembled it when #2 did the same thing. The second time, no doubt as turning off the main power switch inside, did nothing with the starter switch itself being stuck. When the smoke started pouring out of the bellhousing drain hole, I then went an removed the parallel cable. That made it pretty clear where the problem likely was.

My testing now is with a completely different starter and switch (not new, just working originals) and the same thing is happening, switch plunger sticking, even with cleaned connectors.

I read several of the old posts, but didn't see this specifically being addressed anywhere.

Thanks,
Charlie

Post by **wesk** » Fri Jul 06, 2018 7:36 pm

If your body tub is not correctly positioned the Starter kick pedal can wedge itself when starting.

It is extremely uncommon for three different switches of different life spans to fail consecutively on the same jeep.

Some other things to check:

Does the engine turn over freely by hand on the fan and belts?

Does the engine have the ground strap installed at the right front engine mount. If it doesn't it will cause very high resistance in the starter circuit resulting in overheating of the switch and the starter. This is easy to check & you can also connect a jump cable to the block & the frame and try the starter.

If you are running the correct 24 volt starter MCS4301UT on the wrong flywheel tooth count (97 or 124) this can happen as well.

Also there are two adjustment that effect the start switch performance in TM 9-1825B. The actual switch contact position adjustment Par c (4) page 335 and clutch/pinion travel Par d (3) page 336.