M38 Voltage Regulator

Naugha · Post by **Naugha** » Fri Nov 19, 2021 1:15 pm

VBU- 4002UT. Yeah, shot in the dark. This VR thing is going to take some sober effort. Probably no shortcuts.

I should get off my backside and go work on some stuff I can do.

Post by **Ryan_Miller** » Fri Nov 19, 2021 1:29 pm

I guess I missed that older post on Pete!

The eBay VR looks interesting, sure would be nice if they could test those and say if working or not. NOS with rusty feet makes one wonder if it was kept in a moist environment. I know they are supposed to be water proof, but do you think the rubber seals are still good from 60+ years - maybe.

RonD2 · Post by **RonD2** » Fri Nov 19, 2021 1:37 pm

VBU-4402UT. Yeah, big shot in the dark. Besides not having the correct amp rating, I just noticed that the connectors have entirely wrong pin-outs too.

Naugha · Post by **Naugha** » Fri Nov 19, 2021 6:03 pm

“The eBay VR looks interesting, sure would be nice if ...” Ryan

Yeah, the no testing, no warranty, limited (old) parts availability and few folks who know how to fix ‘em makes for a VR challenge.

I think I will fix the wires, paint the box, color the raised letters red, dress the points with a Swiss #6 file (is that found on a Swiss Army knife

), locate the resistors, and start looking around for an old Korean War motorpool vet.

4x4M38 · Post by **4x4M38** » Sun Nov 21, 2021 7:37 am

You could always call Midwest Military and talk to John.

He has always been available to talk about issues.

Naugha · Post by **Naugha** » Sun Nov 21, 2021 11:46 am

I will give John a call next week.... also found a place that offers an interesting twist, new to me at least. Repairs can be done to old VR’s or they can install an electronic VR inside the existing ‘bread box’. Wiring harness and gauge changes would be needed. I am waiting on an email reply from PP.com.

https://www.precision-pwr.com/voltage-r ... erator-cut
“This conversion can be achieved with 100% original exterior appearance.”

One is tempted to get a M38 Auto-lite VR housing and stick a modern VR inside. You would of course need a very, very small sticker on the bottom side of the faux unit explaining you had no idea how to fix the original VR so you spent a lot of money to put a new unit inside an old box.

Much is said in the threads about sacrificing some originality for reliability and drivability. I don’t want a ‘Trailer Queen’ but was trying to stay as original as possible. The old school VR may be a component that will often spoil the fun with few options for repair/replacement. Maybe I should ‘get smart’ on this issue. We shall see.

RonD2 · Post by **RonD2** » Sun Nov 21, 2021 3:43 pm

https://www.eriksmilitarysurplus.com/vore25am28vo.html

Naugha · Post by **Naugha** » Mon Nov 22, 2021 5:39 am

Electronic VR’s.
Always good to have options.

There are many of the old breadbox mechanical VR’s out there for sale that would fit my M38 but they are all untested take offs. Most all of the other rare stuff (carbs/starters/generator/ fuel pumps/ wiring harness) can be bought rebuilt with a warranty. Many repos for almost all body parts/ hardware.

Could a working original M38 VR be the most difficult M38 part to find in proven working condition?

RonD2 · Post by **RonD2** » Mon Nov 22, 2021 8:57 am

Naugha wrote:Could a working original M38 VR be the most difficult M38 part to find in proven working condition?

And pound for pound perhaps also the most expensive.

I've heard it said in this hobby not to add the receipts (or tell your spouse) what you spent, because you don't really want to know that (1) you're well past the point of no return, and (2) you have way more in it than you could ever sell it for.

I've been thinking for some time now that the fastest, easiest, and cheapest way to get a working 24V system is to buy it already attached to a restored M38.

Post by **wesk** » Mon Nov 22, 2021 11:14 am

It's time to put this poor horse to sleep. Traditionally in auto maintenance electrical parts have always had serious warranty restrictions due to their being so easy to damage. That's why all warranties are null and void anytime the tamper seals are broken. Automotive electrical repair and rebuild shops are usually very reliable and the operators have a very thorough understanding of the operating principles. So let's simplify the acquisition of used military 24V equipment. You rarely find 50 year old electrical parts still new in the box and seldom with any kind of warranty. So try to get used the same processes the rest of us have learned to deal with by simply taking the two primary operating parts you want tested to any "Worth a Salt" electrical repair shop and let them do their job. They will bench the gen/reg pair and tell you very quickly what if anything is wrong with them and how to repair and the cost of repair. They have the same, if not even better access to all electrical component service data that we have. If you lack experience or the required skills to repair something then you must take the path we all do and either hire the pro or learn the necessary skills to do the work yourself.

Naugha · Post by **Naugha** » Mon Nov 22, 2021 6:19 pm

“It's time to put this poor horse to sleep..... If you lack experience or the required skills to repair something then you must take the path we all do and either hire the pro or learn the necessary skills to do the work yourself.
_________________
Wes K

Well said. I know my limitations and am willing to hire that pro.
What is his name ?

Post by **wesk** » Mon Nov 22, 2021 11:18 pm

If you read carefully you will see that the name is "Automotive Electrical Repair". Some shops have technicians with more experience than others. You simply ply the yellow pages until you locate a shop with adequate experience. Up here in northwestern Wisconsin I have 4 shops with a 40 mile circle of me that can all handle this work. Keep in mind my nearest neighbor is a half mile away from me.

Naugha · Post by **Naugha** » Tue Dec 21, 2021 3:00 pm

I put the VBC-4004UT on the 'Do Later' shelf and bought this VBC-4002UT.
No guarantee on electronics but the supplier has a very good rep.
We shall see...... moving right along...... one step at a time.

“Thanks for your interest. This regulator is checked carefully by my technician , who is an extremely very experienced electrician with the M series jeeps and trucks. After having checked the regulator is fine , he continues to operate the regulator for about one and a half hours to be sure is working properly and loads correctly.” Steve in Athens

RonD2 · Post by **RonD2** » Tue Dec 21, 2021 3:08 pm

Nice Don!

Tested known good? With a warranty?

Naugha · Post by **Naugha** » Tue Dec 21, 2021 3:36 pm

Hi Ron.

I added some more info above. We shall see.
I do plan to rebuild the VBC-4004UT at some point.

Been spending more time with body work.... cant decide how smooth things should look..... thinking a M38 should have a few bumps, right? Then there is the whole electrical thing & gauges.

Merry Christmas to all.
Don