M38 generator-regulator

1950 - 1952, M38, questions, discussions, regarding anything related to the M38.
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Cannon Cocker
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M38 generator-regulator

Post by Cannon Cocker » Thu Mar 08, 2018 5:11 am

What is the purpose of the plug at the base of the regulator? The data plate is currently covered and I can't share the model number but it's an autolite, 24v. Thanks in advance.

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Re: M38 generator-regulator

Post by Ben Dover » Thu Mar 08, 2018 6:15 am

It's called a "Drain Plug".
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Re: M38 generator-regulator

Post by W. Winget » Thu Mar 08, 2018 6:20 am

Without manuals in front of me, I seem to recall it being an access plug for an adjustment setting if required. Remove plug, adjust output replace plug.
This adjustment was moved to the later altenator near the connection when they did away with the external regulator system.
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Re: M38 generator-regulator

Post by Ben Dover » Thu Mar 08, 2018 7:03 am

Or try this:
Drain Plug, listed in ORD 9 SNL G- ORD 740 and G-758. G-740 calls it OED# 444614, cadmium or zinc plated, G-758 calls it a Pipe Plug, regulator drain. Willys Factory Parts Manual lists it as A-17582 Drain Plug FSN 4730-044-4714.
This Drain Plug is also found on late VRY 4203F and VRY 4203G Generator Regulators installed on MB/GPW.

I peeked at my manuals. This plug sort of gets "honorable mention, it is not discussed in the Auto-Lite TM-9.
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Re: M38 generator-regulator

Post by g.keating » Thu Mar 08, 2018 9:11 am

the solid state regulators have a screw to adjust output


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Re: M38 generator-regulator

Post by W. Winget » Thu Mar 08, 2018 12:35 pm

This is from the M151 manuals, but the system components did not change (much) from mid 50's upward until late 60's.
https://www.steelsoldiers.com/upload/M1 ... 218-20.pdf
Page 3-27:
Para 3-49

c. Regulator Voltage Adjustment (figs. 3-26
through 3-29). Remove plug from top or side of
regulator.
Using a screwdriver, turn the voltage
adjusting rheostat in clockwise direction to increase
voltage and in the counterclockwise direction to
decrease voltage. Rheostat should not allow more
than a 5-volt range in its adjustment and voltage is
to remain stable. Apply sealing compound to
threads of plug.

Ok, no mention of being a drain plug, I don't think they wanted water inside a regulator to begin with. The paragraph before this should be read if trying to do the adjustment, but you just wanted to know what the plug was for.
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Re: M38 generator-regulator

Post by g.keating » Thu Mar 08, 2018 4:35 pm

the regulator referenced in the m151 manual is a solid state 100 amp version. The original post didn't mention he had a 100 amp system but he may. I don't think solid state regulators were ever used on the M38. Below are two links to a 25 amp regulator more readily found on a M38 and the diagram shows part KK. I included the KK part listing. It is a pipe plug.

http://willysmjeeps.com/v2/modules/gall ... _16_PM.png

http://willysmjeeps.com/v2/modules/gall ... _44_PM.png

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Re: M38 generator-regulator

Post by Ben Dover » Thu Mar 08, 2018 4:42 pm

Solid State 100 Amp regulators existed during the M-38 era, many M-38 Jeeps had the conversion. I preferred the 100 Amp Carbon Pile Regulator as the Solid State 100Amp VR by DC Electronics were not reliable even when new out of the box.
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Re: M38 generator-regulator

Post by Cannon Cocker » Thu Mar 08, 2018 6:00 pm

Finally cleaned off the data plate enough to read. It's a VBC-4002UT, 25A. Does this help?

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Re: M38 generator-regulator

Post by W. Winget » Thu Mar 08, 2018 6:28 pm

Flashlight and mirror will answer all...
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Re: M38 generator-regulator

Post by Ben Dover » Thu Mar 08, 2018 7:01 pm

It's still a Drain Plug.
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Re: M38 generator-regulator

Post by Cannon Cocker » Fri Mar 09, 2018 3:25 am

In the event of leakage during fording ops?

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Re: M38 generator-regulator

Post by Ben Dover » Fri Mar 09, 2018 5:28 am

Excellent comment.
The plug can be removed in order to check for moisture and condensation, read your TM "Maintenance After Fording" section. Sealed units can accumulate condensation, removing the Voltage Regulator Drain Plug will allow inspection.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
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Re: M38 generator-regulator

Post by Cannon Cocker » Fri Mar 09, 2018 6:59 am

Thanks much.

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Re: M38 generator-regulator

Post by Ben Dover » Fri Mar 09, 2018 8:34 am

Kudos to the Army for its excellent training.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
7 MIL SPEC MAINTAINED MV'S
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