24-Volt Electrical System Questions...

[mobiledab]

Returning back to MV restoration to provide constructive distraction now that I've retired. Recently purchased a 1951 M37 and expecting delivery at the end of next week. According to the seller, this vehicle has been in dry storage for the better part of 28 years. True or not, the truck is solid and relatively unmolested; however, rear frame rails are bent aft of the cab. It comes with a solid donor frame for future change out. Obvious work will be brake system, fuel tank and electrical system overhaul first, and then I intend to drive and restore over time. As stated in the title, this post is all about the electrical system. I'm not a purist, but also see no point in making changes when things work well as manufactured. I've operated under this premise with every other restoration undertaken and was never disappointed. Unfortunately, whomever put this truck into long-term storage had other opinions.

As best I can determine from pictures, the 24-volt distributor has been replaced by a 12-volt civilian version. That indicates the oil pump was also exchanged for its civilian counterpart. The 24-volt generator (assumed 25-amp) remains, as does the associated voltage regulator on the firewall. I have no idea if the 24-volt starter is there. Oil bath air cleaner is absent, and based upon carburetor airhorn section the ETWI was also exchanged for its civilian cousin (ETWI was found it the bed). Lastly, two ballast resistors with light-colored wiring are mounted to the exterior of the generator voltage regulator bracket. My conclusion based only upon what I can see in pictures is that the 24-volt electrical system is in place, and only the distributor and coil are 12-volt. I feel this is reasonable given the presence of the wired-in-series ballast resistors. I would normally not buy any vehicle without inspecting in person, but I'm disabled from military service and have travel limitations that precluded me from that. All that said, examining pictures from the current owner are the best I can do until the truck arrives. It's been quite some time since I've worked on 24-volt systems and was not an expert even then. I'm hoping those of you who have stuck with your passion for MVs can give me some much-needed counselling!

Is the 24-volt generator still rebuildable, meaning all necessary parts are available to servicing shops?

Same question for the 24-volt starter. If memory serves me correctly from my M37B1, changing to a 12-volt starter means changing out the flywheel for the correct number of teeth.

I found a solid state generator voltage regulator and wondered if any of you have modified your 24-volt system with one? Is it a good upgrade or should I steer clear? Is it just a simple swap part-for-part?

How well does the system work if I leave everything at 24-volt potential but the distributor, coil, etc.? I would probably not use ballast resistors and replace then with a solid state 24- to 12-volt DC regulator with adjustable/fixed amperage output--3 ohms target/minimum!

Would it be best to eliminate the OEM circuit breakers and add inline fuses on critical circuits? Although I never had a significant wiring issue, I recognize they happen. I would completely rewire with the frame swap so this would be an interim and preparatory step in the interest of safety and dependability.

Still have crimping tool from military service for Packard connectors. I plan on primarily employing Packard connections to the greatest extent possible in the rewire; however, I'm a great fan of using marine-grade tinned copper wiring vice the military wire. Does anyone have strong opinions to the contrary? I'd welcome any thoughts or recommendations. My only reason for preference comes from experience building harnesses for cars and boats and this wire holds up extremely well.

Finally, has anyone else had success with frame straightening? Only time I've had it done professionally was on my WDX and insurance was paying for it (someone hit me). Any other time was using a frame machine I had access to. Since that frame machine is now in Colorado and I'm in New York, it's no longer an option. Best I can do now is use a HD construction equipment trailer as my pulling/anchoring base with jacks/jack stands/steel I-beam to keep the axles off the ground. Pulling is easy with a chain binder, and pushing with jacks from the trailer as a base. Also may have the option to use an offroad forklift as a relocatable bracing base to push or pull from. I know not to heat frame rails unless a last resort. In any case, the adjusted areas will be braced by welded steel patches. This is just so I can keep driving the truck while getting the donor frame prepped for swap out. I really do love these trucks and missing having one to drive. My wife thinks I'm crazy!

Thanks for any wisdom or experience you care to share. Any and all will be greatly appreciated!

Best regards,

David

 

[ab705]

Thanks for any wisdom or experience you care to share. Any and all will be greatly appreciated!

You should be able to find a 24V ignition coil. The distributor doesn't care about the voltage.

You might consider a Pertronix breakerless ignition conversion. I would call Pertronix and tell them exactly what distributor model you have, and mention that the system is 24V. They may be able to come up with something for you.

You could consider going back to an OEM waterproof M37 distributor. See if there's one in the spare parts that will be coming with your vehicle. Maybe there's still a set of waterproof sparkplug cables. That would require the appropriate oil pump to match the distributor drive tang. One downside to going back to the original ignition setup is that replacement waterproof cables and sparkplugs are rather pricey, unless you find a good used set, although I've seen people use ordinary cables and plugs with the M37 distributor. There are also standard-to-waterproof plug conversion shells available, but I don't remember where I saw them.

Unless there is a short in the 24V generator armature or field, it should be good for a long time. Brushes and bearings can be replaced if they're worn. Used generators and parts are an option as well. There should be quite a few working 24V used generators available. You can get rebuilt 24V generators, but expect to pay a premium for them. A local generator shop might also be able to overhaul it for a better price.

If you're using Packard connectors, when you order wire, make SURE that the outside diameter of the insulation is large enough to seal snugly in the wire openings of the rubber Packard connectors, or else they won't be water resistant. I ordered mil-spec wire with tinned copper strands. It's nice and flexible, like the original rubber-insulated wire.

As to frame straightening, I've dealt with that on a couple of antique trucks years ago, but I couldn't venture a guess regarding yours without seeing exactly what is bent, where it's bent, and how it is bent. Individual cross-members are available, used or, in some cases, NOS members. Rivets can be replaced with appropriately selected and sized bolts. Depending on the damage, it might be easier to prep the donor frame you mentioned (such as sandblasting/priming/painting), and then transfer everything over to it, doing any repairs/mods/cleanup to those items as you install them. It's actually kind of a luxury to be able to start with a bare frame if you're doing a total restoration. There is the matter, of course, of a different serial number on the donor frame. Before you consider going ahead with the donor frame, I'd call your state Motor Vehicle Division and see what would be involved in updating or replacing the registration and/or title with the different serial number.

 

[mobiledab]

Thanks for replying--I was concerned no one would given the subject must come up often!

As for the coil, my understanding is that current flux/or current being too high was an issue. Again, I'm no electronics wizard--had remembered reading somewhere that the magic current was no more than 3 amps. Is that a concern or did I misunderstand?

I'm familiar with the Pertronix offering and it was installed in my WDX Power Wagon--quite an improvement and it eliminated a miss problem that kept recurring.

I am really leaning more toward restoring back to 24-volt. Having a so-called "mixed bag" just complicates things. Good news is although the military distributor body and shaft is missing, the outer cap and and waterproof cables were found in the bed along with the ETWI carburetor. Unknow what else may be hiding under the canvas and troop seats, but it will be my first task when the truck arrives. Was unaware of the standard-to-waterproof conversion shells, but will research.

This coming week I'll make some calls about having the generator gone through locally. We live outside Rochester, NY and there exists a strong network of commercial truck as well as heavy construction equipment repair facilities here. My hope is that includes a shop who is experienced in electrical systems. If not, Buffalo and Syracuse are large cities who may have local expertise if Rochester does not. Have read multiple posts on forum platforms where many MV owners have had success upgrading to Delco 10Si 24-volt alternators. That would eliminate the generator, generator voltage regulator, and require swapping out the dash ammeter for a voltage gauge.

Understand about the Packard connectors. Have learned the hard way that some vendors will sell anything without concern for how well it meets the end user's requirements. Regarding the wire, I now only buy from US sources that stock US manufactured product. The most painful lessons are those we don't (or refuse to) learn from!

Although I'm hoping to drive this truck for awhile and restore over time, I have to admit that may not be possible if the frame damage is too severe. I won't know until we can get the bed off and have a close look. As best I can tell, damage is aft of/begins at the crossmember for the front mount of the rear spring mount, passenger side worse than driver side. Both frame rails appear to be involved. Looking from the side the bed his down several inches at the rear. From the rear both frame rails appear to be even. The current seller thinks someone dropped too much trailer tongue weight on the pintle (which is conspicuously absent) and then put the truck in storage. Unless the bed was changed out after-the-fact, it's possible given the bed floor looks perfect and absent of any damage.

As you highlight, working on a bare donor frame will be to my advantage. You are correct--NYS will be a problem insofar as getting this registered and plated. NY State Police will do a VIN/serial number investigation and the DMV takes it from there. The truck is coming from another state only with a BOS and no title. In NY it would be too old for a title, but one from another state would make things much easier. Another person I spoke with shared it took him almost a year to get a transferable registration from NY DMV for his M37. As long as I can get a nontransferable registration in the mean time it will be fine.

Again, thank you for your reply and advice! I value and appreciate it greatly!

David

 

[ab705]

It shouldn't be hard to find a good used military distributor body and oil pump, especially since quite a few people have M37s with civilian ignition, hence some spare take-outs should be lying around. As to coil operating current ranges, that can vary. The coil manufacturer should be able to give you some information about that. At any rate, if you're running a 12V coil in a 24V system, you will probably need two ignition resistors instead of one (a lower-resistance one for starting and a higher-resistance one for running).

Did the seller provide a photo of the serial number that's stamped on the frame? The serial number on the glove-box data plate isn't always reliable, as the plate or glove box door may have been changed at some point. It gets more complicated if the M37 had been converted to a different variant (such as an M42) by the military and then converted back to an M37 before releasing it to another agency or public sale, which is apparently the case with my M37. If you happen to require a state inspection to view and confirm the serial number for some reason, they'll almost certainly want to look at the number stamped on the frame. That's why I mentioned that if you change frames, you'll be changing serial numbers, regardless of the data plate on the glove box.

Years ago when I was living out west, a friend and I registered a Model T Ford that we were working on together. There was no title, and to get a title, someone (from the DMV, IIRC) had to come out and check the serial number in person in order to sign off on the title application.

I don't know what the NY requirements are for registration or titles. Here in Maine, my 1954 M37 is old enough that a title is not required, although I do have an out-of-state title for it. I registered it a little while ago as an antique vehicle. I just started posting some of my restoration activities here on this forum.

More on wire: I bought some 14-gauge Southwire automotive wire a while back, but the outside diameter of the insulation was too small for the 14-gauge Packard connectors to seal against. So even high-quality wire still might be too small for the Packard connectors. The 14-gauge mil-spec wire I bought has thicker insulation and seals well.

Overhaul kits are available for the ETW1 carburetor. The ETW1's governor can be a little touchy to adjust, but not really difficult. It's not a bad idea to have an operational governor.

 

[mobiledab]

Valid points regarding the distributor and coil. Gives me even more incentive to go back with the military as-built 24-volt system. It worked! My only possible change would be the Pertronix kit. Fingers crossed that the 24-volt cap and cables are sound and can be used.

No photos of serial numbers. I do have pictures of the donor frame itself, and several under the truck highlighting the frame damage. The truck was advertised as a 1953 as that is what the seller was told when it bought the truck. I asked him to relay the data plate information and that's when we discovered it was in actuality a 1951. Shown on the plate is model M37 without winch, serial number 80010678, and a manufacture date of August 03, 1951. That serial number is not found in the registry and that leaves me at a dead end (for now) with respect to tracking down prior owners. The donor frame itself is from a 1953 according to the seller. Frame rails for M37 and M42 are not just shorter than M41 and M43--they are thinner. In any case it's coming with the truck and third on my list that day is to measure the frame to confirm it's not tweaked and will work as an M37. NYS does have an inspection that must be passed, and from experience I know the NYSP will look to the frame first as you point out. I will not be able to do anything registration wise until after the NYSP do their inspection and give me a completed form for DMV.

I've been trying to read and note progress on multiple ongoing restorations on a number of sites. I will be looking for your posts now as well! One very impressive one of a CDN M37 on the Maple Leaf Up site. Lots of detail and clear, high resolution pictures.

There are Packard connectors out there coming from China and I try to be very careful about everything I source--not just for restorations. The marine wire I prefer to use is Ancor brand. As you point out, not all wire is created equally. There is a difference between SAE (typically automotive use) and AWG (typically marine and industrial use) ratings. SAE wires are smaller in diameter and carry less current before they melt because of that. It may also be up 10 percent smaller than AWG wire and therefore carries 10 percent less current. Who knew? I did not and found out the hard way. Since Packard connectors are designed and manufactured to MIL STDs (or are supposed to be), you should never come across disparities. Unfortunately we do--even when using military specification wire--because not all sources play be the rules.

As for an integrated governor, my WDX had one, just a different Carter B&B one-barrel model. It was very difficult to find kits and/or a replacement at the time given anyone who had a good one was using it. At the time and for a Power Wagon it was just as rare and elusive as the rear PTO pillow block for farm implements. It was similar to those used for same purpose on period Jeeps, but those for Ford tractors would come close. Took me 18 years of owning that truck to find an original with the correct rear PTO shafts out in eastern Colorado. It was less than a month later that another one was listed in Maryland. I bought that one, too and have never seen another one for sale since. Both went with that 1946 WDX when I sold it in 2014. Like most vehicles I've owned that is one I wish was never sold. Will rebuild the removed ETWI in the bed and keep the civilian version on the truck to see if it will run. Still looking for a correct oil bath air cleaner that supports a fording kit. Don't have either (air cleaner or fording kit) but will be searching for both (whole or in pieces). May just design and assemble my own version. I no longer have a production plasma table (again, sold with moving), but have been using a service out of Nevada called "Send Cut Send" as they offer manufacturing services that eclipse what I can avail locally. In other words, they are one-stop shopping at reasonable prices and free FedEx or UPS shipping. They have satellite facilities across the country and orders can be tracked from start to finish. If anyone is good with CAD/CAM software (AutoCAD, SolidWorks, QCAD, etc.) and can output DWF/DWG/SVC files should take a look at their offering and web site.

Thank you again, and I will post pictures/progress once the truck and frame make it to NY!

David

 

[ab705]

The Southwire automotive wire and the mil-spec wire I bought are both AWG 14, but the mil-spec wire has Hypalon insulation that is not only thicker, but more flexible than the Southwire, which has PVC insulation. I don't like working with stiff wire. Here's where I bought the mil-spec wiring:
https://www.wiremasters.com/product/M13486-1-5
I thought their price was quite good. I bought 200 feet of this wire. I don't know if they have a minimum purchase or not.

Here is a site that provides some specifications for the wire:
https://www.awcwire.com/product/m13486_1-5

Here's the link to my restoration thread (it's fairly short, so far). It's right in this section of the forum:
https://www.steelsoldiers.com/threads/m37-restoration-project-revived.219891/

I have a plasma cutter, but no room at the moment for a plasma table. If/when we get our second garage built, that may change.

 

[mobiledab]

I agree on flexible/pliable wire. That was the reason I began a search for widely available wire that had a variety of colors. Color options and Ancor quality were big influencers. Although I'm passing on Painless and other such kits, color trumps black wire with tags.

Also, turns out I had already viewed your restoration and was quite impressed! Your attention-to-detail is awesome! Interesting to see your perspective on what you've accomplished thus far. I went back and annotated appropriately!

One question I had was about the copper-nickel brake line. Is the product widely used? It's new to me and that's why I'm asking. Planned on buying the pre-made steel lines to get the truck back on the road, but thinking ahead about completing the donor frame.

The military-issue crimper I have for termination is old, but the operation and ergonomics appear to be almost identical. One thing for sure, your crimper looks to be far better quality. Where did you find it?

My production plasma system was huge. Bought it from a company named TorchMate and it was one of their early models with a water table. Frame was made of extruded 4x4 and 4x6 extruded aluminum (80/20 is similar); table afforded 6' wide by 12' long with an additional 6' long extension (made with parts from 80/20). Cutter was Hypertherm Powermax 85 and the table used TorchMate's proprietary software. Bought it as an investment as at the time there were no such businesses in southern Colorado. Huge financial investment, but it was a money maker--especially doing custom 2-D steel figures/signs/logos/etc. The table also had the ability to laser locate, pneumatic engrave and with the table extension cut from full sheets. Extension also afforded ability to index next sheet for large pieces or large numbers of nested identical parts. Disassembled and moved it here to NY, but had no place to go back in business. Took a long time to get a house built, so I sold it to a guy in Canada. We are close to Ontario province so he just drove down. Miss having the capability, but there's no way I could do the work physically anymore. Send Cut Send is very good, and if I need something in a hurry there's an awesomely talented young fabricator with a similar table not far away. A 4x2 to 4x6 home table setup would be awesome and doable; however, I'd rather spend the money elsewhere now. A hand plasma torch like a Hobart or Lincoln is very handy for these restorations! Unfortunately I just can't do too much anymore. I'll be imposing a lot on my wife and neighbors--or spending money paying somebody else to do what I can't.

Thanks, and I'll figure out how to follow your restoration in the morning!

Best regards,

David

 

[ab705]

I agree on flexible/pliable wire. That was the reason I began a search for widely available wire that had a variety of colors. Color options and Ancor quality were big influencers. Although I'm passing on Painless and other such kits, color trumps black wire with tags.

Color-coded wiring is a very nice way to keep things in order without having to fuss with meters or tags. That said, my plan for my M37 is to keep it primarily original, other than a few safety mods, so I'm staying with original-type black wiring.

One question I had was about the copper-nickel brake line. Is the product widely used? It's new to me and that's why I'm asking. Planned on buying the pre-made steel lines to get the truck back on the road, but thinking ahead about completing the donor frame.

CuNi brake line is becoming quite popular here, and it's been in use in Europe for decades. It's approved, bends easily, corrosion resistant, and easier to double-flare than steel lines. I buy US-made line that has a little thicker wall than some of the imported stuff I've seen.

The military-issue crimper I have for termination is old, but the operation and ergonomics appear to be almost identical. One thing for sure, your crimper looks to be far better quality. Where did you find it?

The crimper was an eBay purchase. It came with a full set (for this particular kit) of three wire guides, two of which were stored in the hollow handle of the crimper. I'm looking for a reasonably priced crimper for what I would call the female terminals used in the male Packard connectors. A lot of people use the four-prong crimpers for both types of Packard terminals, but as you might have noticed, I found a reference to a different kind of crimp tool die for the female terminal in the male connector. I think I found something that will work, and if/when I'm sure it will work, I'll post it on the forum.

BTW, I'd love to have the plasma-cutting setup you described, but no space (or budget) for something that fancy. Maybe a small table someday. I have a manual Miller plasma cutter that works well for my projects, as I'm not doing any production work...mainly just one-off things for myself.