M38 generator 24V measure

1950 - 1952, M38, questions, discussions, regarding anything related to the M38.
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Winni_M38
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M38 generator 24V measure

Post by Winni_M38 » Sun Nov 05, 2017 2:17 am

Hi,
this is my first post here on G503. A very huge and active forum. Thanks for take part on this.

After some CJ 5 with 4- and 8-cylinders I bought some weeks ago a M38 1952. I knew the T90 and D18 need some work, but the Jeep drives with some noise. Not really big problems. But now the generator wouldn`t work and don`t charge the batteries. After my last drive I realized the signals does`t work and the engine don`t starts. The ignition and electricity was completely taken by the two batteries.
My question is, how to measure the generator and regulator with a multimeter? The Prestolite gen. has so very fat cables which are capsuled so I cannot take a look direct to one cable.
Does anybody know what is to do?
Thanks in advance for your support from Germany.
Jörg
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mdainsd
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Re: M38 generator 24V measure

Post by mdainsd » Sun Nov 05, 2017 8:08 am

Hello and welcome t the forum.

To really measure what is going on in the charging system, there is a set of special adaptors that allow you to access the wires in that big cable.

But you can find out what is going on fairly simply. Charge the batteries back up. Connect your multimeter across both batteries. Should be around 24 volts if the batteries took a charge. Leave the meter on there. Start the engine, and once its running look at the voltage. What is it?

Turn on the headlights and increase the RPMs to fast idle or a bit more, 2000 revs is plenty. Look at the meter, it should be close to 27 to 28 volts. If it is still at the same reading or lower than what you first started with then the charging system is kaput (I could not resist).

To determine whether it is generator or regulator, you will need to source those special adaptors, probably.

Winni_M38
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Re: M38 generator 24V measure

Post by Winni_M38 » Sun Nov 05, 2017 10:10 am

Hi mdainsd,
thanks für your quick response.

Let me explain it with my words to understand right:
1. charge both batteries with an external charger
2. connect the voltmeter's (+) with the (+) of battery nr.1 and voltmeter's (-) with the (-) of battery nr. 2 = this is the 1st measurement and schould show 24volts in the voltmeter
3. same like 2. and start the engine = this is the 2nd measurement
4. same like 3. and switch on the headlight = this is the 3rd measurement
I will tell you....
M38 1952 coloured sand

mdainsd
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Re: M38 generator 24V measure

Post by mdainsd » Sun Nov 05, 2017 11:56 am

Yes you have it right!

Report back with readings.

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skyjeep50
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Re: M38 generator 24V measure

Post by skyjeep50 » Sun Nov 05, 2017 3:22 pm

You may also want to check out the Willys M Jeeps website www.willysmjeeps.com There in the "Downloads" section you will find complete technical manuals plus additional information that you can use to troubleshoot your M38. In the photo section there are additional technical photos of owners projects and vehicles. Very good resource.
1 - M38
1 - M38A1


Winni_M38
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Re: M38 generator 24V measure

Post by Winni_M38 » Mon Nov 06, 2017 12:00 am

Yes thanks for that. I‘ve seen it and made the registration but get no email with confirmation. If I use the „forget passwort“ the system needs my nickname. Sorry, I haven‘t write it down and only with an email adress you are not allowed to set it back - hm, difficult to take part on that side
Last edited by Winni_M38 on Mon Nov 06, 2017 12:02 am, edited 1 time in total.
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Winni_M38
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Re: M38 generator 24V measure

Post by Winni_M38 » Mon Nov 06, 2017 12:01 am

To be clear: the problem is in front of the keyboard here in Düsseldorf;-)
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mdainsd
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Re: M38 generator 24V measure

Post by mdainsd » Mon Nov 06, 2017 11:17 am

See if you can locate department of the army publication: DA Pamphlet 750-33

It is a detailed way to trouble shoot the military generators and regulators.

Winni_M38
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Re: M38 generator 24V measure

Post by Winni_M38 » Mon Nov 06, 2017 7:45 pm

Thanks! I have downloaded it from the Web. Also I found the Admin-mailadress of willysmjeeps.com and asked for refresh my account.
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