Bob M and wiring / 12 volt conversions.

I am trying to find both an alt. for a farmall M that will charge at low RPM and not have to cut hood,as well as a complete sketched wiring diagram for a farmall m with magneto and will have lights on light bar as well as rear light. The tractor currently has no lights or electrical so I am starting for scratch and will also need a new light switch, have heard they have both 3 and 4 position?? Any and all help or feed back will be appreciated.
 
This will fill the need. Note the wire gauge. Jim
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Bob M diagrams
 
If done right a simple Delco 10si will fit. I use an alternator made for a 1980 Chev pick up no power any thing no AC. Done more then one on an H and an M
 
Hitachi 14231 is a nice small alt
The S terminal is = to the delco #2
the L terminal is = to Delco #1 terminal Jim
 
Plain old Delco 10SI alternator works just fine at low RPM.

No need to cut the hood either. There's plenty of room.

There are advertisers in Red Power magazine that sell a complete kit including a bracket that positions the alternator. If you're starting with nothing this is probably the way to go.

If you have a generator bracket, you just need to know a couple of simple tricks to make it fit:

1. Install the generator bracket upside down.
2. Use 3/8" all-thread to mount the alternator ahead of the bracket.
3. You may need to hacksaw off a small bit of the lower mounting lug on the alternator to get the belt to line up, or shim it out with washers, depending on the alternator you get.
4. You may need to grind a "divot" in the front arm of the bracket to get the alternator to sit right.
5. The stock length belt works fine with the alternator.
6. The back half of the alternator can be "re-clocked" so the wires point out in a convenient direction. Just remove the bolts and carefully rotate the back half 90 degrees, then put the bolts back in.
 
A few more comments:

With an alternator conversion you need only a 3-position light switch. (A 4-position switch works but is not required)

A 10SI alternator fits easily under the hood of an M.

If you can, get an alternator with the LOWEST output rating you can find - 37 or 42 amps is good. (Output amps is stamped on the case along with "12 V NEG" and the part number). Reason: Higher output alternators need higher RPM to turn on after startup.

Also us the SMALLEST pulley you can find on the alternator so it spins as fast as possible.
 
I used the Hitachi on an M and on my 400 like Jim said. I am sure you can make a delco fit but the hitachi is smaller and the same price.

I just flipped the generator bracket over drilled it and the alternator out to 1/2 inch to take threaded rod with nuts to center it all up and tighten everything. Top bracket I used an old alternator top bracket for the long adjustment slot and welded or bent it to fit.
 

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