Home Hi,
First off, I was taught to never speak ill of the deceased. This is an important point. Now for the whole story:
I bought a M37B1 a couple years ago. It had undergone a V8 transplant. The newer engine is a Dodge 318A from the 1960’s. It was quite the shoehorn of a job. I’m not sure of all the mods but the ones I know about are:
1. Obviously the V8 stuck in the engine compartment.
2. Generator replaced by a alternator.
3. Carburetor is a two barrel Motorcraft originally from a Jeep.
4. It has a dual exhaust.
5. Power steering installed. Yeah, I’ll leave that alone for now. I’d really prefer an original horn button.
6. It had a very unique hydraulic hoist installed in the aft right corner of the bed. I’ll leave that one alone as well.
7. A rats nest of a wire harness... remember, do not speak ill of the deceased...
8. A heater was shoehorned up under the dash. Nightmare? Yes.
9. Two dash electric horns installed in grill. One doesn’t (didn’t) work. They’re gone.
10. I can’t, for the life of me, figure out how the electrical system’s worked!
11. The entire 24 volt systems were removed. 12 volt stuff stuck in its place.
There’s more. As I remember them, I’ll add them to the list.
What I’ve done so far:
1. removed all of the wiring,
2. Removed the stater switch (keyed),
3. Removed the fried starter relay,
4. Removed the entire heater set up.
5. Replaced the ballast resistor,
6. Replaced the coil,
7. The truck had a solid bumper installed and has a winch installed as well. The stock two-winch bumpers was reinstalled. The winch was left alone,
8. There’s more but my brain is getting mushy.
My problem: wiring isn’t fixed. I had to remove and replace every wire for stem to stern, bumper to bumper, all of them.
In their place, I patched in a mostly complete original M37 wiring harness. A lot is self explanatory. A lot is completely baffling. I tested every component as best I could using a multimeter. There was a couple parts that were broken.
After deciphering the M37 harness diagram and a couple D200 harness diagram, I was fairly certain what I needed to do. Everything went in its place except for the few wires that were no longer necessary. I hooked everything up then very careful hooked up the battery. Nothing. Not a peep.
Initial troubleshooting leads me to believe the problem is in the power feeds to the harness. Specifically wires #10 and #12. I just can’t figure how to hook them up. Any suggestions are appreciated.
Has anyone done a mod like this? If so, how to I get power from the source (battery) to the entire
Doing a complete rewire on a V8 moded M37
Moderators: Cal_Gary, T. Highway, Monkey Man, robi
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jeffhuey1n
- Posts: 1
- Joined: Mon Jan 04, 2021 2:16 pm
Doing a complete rewire on a V8 moded M37
Proud owner of a M-37, M1009, 3 M35A2’s, 2 M211’s, a M52A2, a G506 fire truck. Also have a M59 dump truck but it’ll be going to a better home soon.
Re: Doing a complete rewire on a V8 moded M37
Hi Jeff,
My goodness you have your hands full! That's quite a laundry list you've compiled from the stuff already hacked, then what you've done for recovery.
Obviously it's your truck to do with what you want-the first question is to answer just what you want out of the truck? Frame-off resto, parts getter, farm truck, parades, shows, etc.? Once you answer that, then you can build out your plan.
I sense an aversion to going 12V; however, many of us including me run 12V systems. Mine already had 12V components so I stayed with them and upgraded my wiring harness (Painless Performance), high-rev starter (Charles at M-Series Rebuild LLC), GM alternator, etc. Those were much less expensive than going back to 24V, and in my case, with so few HMVs around here in the Salt Lake City area I like the security of getting jumped should my batteries fail on the road.
You can find the early and late wiring diagrams here that should address your questions regarding wires 10 and 12:
http://www.g741.org/PHPBB/viewtopic.php ... NG+DIAGRAM
Good luck with your project! I'll leave some room for the others to weigh in!
Gary
My goodness you have your hands full! That's quite a laundry list you've compiled from the stuff already hacked, then what you've done for recovery.
Obviously it's your truck to do with what you want-the first question is to answer just what you want out of the truck? Frame-off resto, parts getter, farm truck, parades, shows, etc.? Once you answer that, then you can build out your plan.
I sense an aversion to going 12V; however, many of us including me run 12V systems. Mine already had 12V components so I stayed with them and upgraded my wiring harness (Painless Performance), high-rev starter (Charles at M-Series Rebuild LLC), GM alternator, etc. Those were much less expensive than going back to 24V, and in my case, with so few HMVs around here in the Salt Lake City area I like the security of getting jumped should my batteries fail on the road.
You can find the early and late wiring diagrams here that should address your questions regarding wires 10 and 12:
http://www.g741.org/PHPBB/viewtopic.php ... NG+DIAGRAM
Good luck with your project! I'll leave some room for the others to weigh in!
Gary
Cal_Gary
1954 M37 W/W
MVPA Correspondent #28500
1954 M37 W/W
MVPA Correspondent #28500
Re: Doing a complete rewire on a V8 moded M37
Hi Jeff,
It’s hard to offer pointed advice without seeing the truck in person, but what I have a couple thoughts.
1. You may have everything wired up properly, but running into issues with a poor connection somewhere.
2. Sometimes replacement electrical parts can be bad right out of the box, so make sure to test them.
3. A multimeter is probably your best bet here. When you have the battery hooked up, start checking for voltage along the harness. Check the new starter relay and make sure it gets power, and the signal to start.
4. Don’t forget grounds. A bad ground can give all sorts of trouble, even if it “looks” good. Clean the straps and the mountings with a little sandpaper.
Hope this helps. Sounds like you have a pretty good idea of what you’re working on, so my apologies if this is pretty basic advice.
Good luck,
Rob
It’s hard to offer pointed advice without seeing the truck in person, but what I have a couple thoughts.
1. You may have everything wired up properly, but running into issues with a poor connection somewhere.
2. Sometimes replacement electrical parts can be bad right out of the box, so make sure to test them.
3. A multimeter is probably your best bet here. When you have the battery hooked up, start checking for voltage along the harness. Check the new starter relay and make sure it gets power, and the signal to start.
4. Don’t forget grounds. A bad ground can give all sorts of trouble, even if it “looks” good. Clean the straps and the mountings with a little sandpaper.
Hope this helps. Sounds like you have a pretty good idea of what you’re working on, so my apologies if this is pretty basic advice.
Good luck,
Rob
Re: Doing a complete rewire on a V8 moded M37
very good advises. I would add if permitted to test the harness by running a 15w or more bulb instead of testing continuity of measuring voltage with a multimeter.
the best test is measuring volt drop but if you connect a bulb and it glows up perfectly bright then you have good voltage supply!
as I said the correct way is by measuring voltage drop with a multimeter lightning a bulb. whith that you measure the resistance from both the bulb and the one from the wire and its pins etc. but that it is more than we normally do so just watch for a bright bulb and it will be perfectly good tested!!
Ronnie
the best test is measuring volt drop but if you connect a bulb and it glows up perfectly bright then you have good voltage supply!
as I said the correct way is by measuring voltage drop with a multimeter lightning a bulb. whith that you measure the resistance from both the bulb and the one from the wire and its pins etc. but that it is more than we normally do so just watch for a bright bulb and it will be perfectly good tested!!
Ronnie
Re: Doing a complete rewire on a V8 moded M37
jeffhuey1n,
Here's my thought. Start simple.
Ignore anything that is not necessary to get the truck to run and build up from there, system by system. Keep non essential stuff out of the mix until you have the essentials sorted. Also be ready to cut power if there's some kind of short that you are unaware of.
The thought of grafting multiple wiring harnesses sound like a PITA, but if you do it system by system it should work out.
Andy
Here's my thought. Start simple.
Ignore anything that is not necessary to get the truck to run and build up from there, system by system. Keep non essential stuff out of the mix until you have the essentials sorted. Also be ready to cut power if there's some kind of short that you are unaware of.
The thought of grafting multiple wiring harnesses sound like a PITA, but if you do it system by system it should work out.
Andy
Re: Doing a complete rewire on a V8 moded M37
ther is a video un YouTube from a guy doing that. hi bough a general purpose wiring barnes for dont remember what if dragster or hot rods or something. he vives some good advises too. let me find it for you.
Re: Doing a complete rewire on a V8 moded M37
My Painless Performance harness instructions advised to test with the 2 amp side of a battery charger. That way if you got something backward it won't fry your harness. Andy is also right in starting with the engine/ignition part then going from there. Painless uses the same methodology in their instructions.
Gary
Gary
Cal_Gary
1954 M37 W/W
MVPA Correspondent #28500
1954 M37 W/W
MVPA Correspondent #28500
Re: Doing a complete rewire on a V8 moded M37
Keep in mind the original loom used the voltage regulator as a pass-thru from battery to system. Unplugged, no power anywhere.
Since that is all gone, and you have an original M37 loom, do you still have the 4-pin Bendix plug?
You may have to cut off the plug and connect the 12V battery positive to the ends.
PoW
Since that is all gone, and you have an original M37 loom, do you still have the 4-pin Bendix plug?
You may have to cut off the plug and connect the 12V battery positive to the ends.
PoW