Spooky electrical problem M38

tomsetterwall · Post by **tomsetterwall** » Sat Aug 17, 2019 7:55 am

Hi,
I have a 1952 M38 in very good condition, but have been having some electrical issues lately. The jeep still has its original waterproof system.
The problem started with a "slow" starter and still good batteries ( I thought) I removed the starter switch and the contacts were really bad. Changed the switch but the problem was not solved. Changed the starter to a NOS one, same problem....
Took a closer look at the batteries, and one of them was bad. Changed the batteries and now I really got things going! So far, so good.
I towed the jeep to Normandy and participated in the 75th D-Day anniversary for about a week and had the opportunity to drive all over the place with a couple of buddys. Everything went smooth and it was great fun.

A couple of weeks ago the jeep stopped when I was out driving. A friend towed me home. Changed breaker points, capacitor, coil (The jeep got new spark plugs and NOS ignition cables before the Normandy trip.)
I changed all the internal cables in the distributor also and even the radio interference capacitor.

The jeep still would´nt start.. I checked all the connectors under the dash, and still nothing suspicious. I finally found the problem in the coupling that connects the + from the starter to the alternator. The + cable was almost in half and the insulation gone close to the coupling.
I removed the old cable with a new one, and when I tested if I had current from the starter via the alternator to the + cable to the ignition switch, it was full flow. Finally I thought I´ve solved a long and expensive problem.

Now to my spooky problem (I´m not really a mechanic, but I´m learning every day)
I have full flow in the + cable in the engine compartment, but when the cable passes the firewall its dead! It seems like a magnetic problem?!
I don´t really know what to do now, except asking for your knowledge at this excellent site.

Thanks in advance!

Tom in Sweden

Post by **wesk** » Sat Aug 17, 2019 10:02 pm

Hello Tom,

You definitely have had your share of problems. You haven't given us enough information to help you. I would like you to verify either you have the original 25 Amp DC generator or do you actually have an AC alternator in the 60A or higher version? Your identification descriptions of some of your wires leaves me not being sure which you are discussing. It would be a lot more help if you use the wire numbers found in the wiring diagrams.

This would be the stock factory original wiring for the 1952 M38.

If you do have an alternator then please show us how it is wired to your jeep and identify which alternator it is.

This illustrates the changes made for the 60 amp alternator kit.

This illustrates the 100 Amp alternator wiring.

tomsetterwall · Post by **tomsetterwall** » Sun Aug 18, 2019 1:38 am

Hi Wes,

Thanks for your kind reply. I will take a closer look at the jeep tomorrow and get back to you with the needed info.

Have a great sunday!

Tom

charlesfitton · Post by **charlesfitton** » Sun Aug 18, 2019 9:46 am

I'd be taking a serious look at the ground

tomsetterwall · Post by **tomsetterwall** » Sun Aug 18, 2019 3:21 pm

Thanks Charles, I will..
Tom

tomsetterwall · Post by **tomsetterwall** » Mon Aug 19, 2019 11:43 am

A short update:

My jeep has the 25 amps 28 VDC regulator, and the cables I was referring to was # 4 Voltage regulator output and # 10 that (at least in my jeep has been connected to the circuit breaker)

It seems that the spooky partner in this was me....
Did´nt ground my test light like I thought I did when I left the engine compartment.

I now have current in full flow into the dashboard and ignition switch, but when I tried to start the the jeep it would´nt start. Disconnected the # 12 cable and tested if I had current to the distributor, and I had! Whoaa!

I´ll check for spark tomorrow and get back here.

Cheers from Sweden

Post by **wesk** » Mon Aug 19, 2019 2:43 pm

the cables I was referring to was # 4 Voltage regulator output and # 10 that (at least in my jeep has been connected to the circuit breaker)

#4 is actually power "INPUT" to the voltage regulator. If you disconnect #4 from the starter then 10 will not have any power on it.

When you say:

but when I tried to start the the jeep it wouldn't start

does this mean the starter did nothing or does it mean the starter turned over slow as before and the engine still failed to start?

A slow turning starter can be caused by several issues:

1 - Weak batteries.

2 - The starter itself, Hi resistance inside the starter's switch, worn brushes or worn bearings.

3 - Bad or loose grounds. Primarily we are talking about the battery cable connections to ground and the starter's connection to ground. There is a heavy braided ground strap for the engine accessories between the engine's right mount and the frame.

Make sure you have the starter's front support bracket installed.

4 - Battery cable connections loose or corroded.

5 - Ignition timing advanced too far.

tomsetterwall · Post by **tomsetterwall** » Tue Aug 20, 2019 10:08 am

Hi folks!

Finally my "spooky" skills as a mechanic + a friend paid off....
Thanks to all good pics from Wes and your kind thoughts, and my friend with electrical skills solved my M38s trouble.....

I´ve cleaned all contact surfaces for - like in Wes pics, changed all the battery cables to new ones before my electrical friend found out that ther was a to large gap between the breaker points.

He also helped me with a short circuit on the back side of the instrument cluster.

I took her for a spin in quite good weather here in southern sweden today.
Everything worked just fine.

THANKS FOR YOUR KIND SUPPORT!!

Tom