MM R wiring/ battery

Larry Metzgar · Jun 2, 2014

I am restoreing a Minneapolis Moline RTU. It appears to be a 1947. Is this a 6 or 12 volt system ( Battery). Is it a positive or negative ground? It is not going to be a show tractor just one we use around the farm. Anyplace special where I should get a wiring harness? Thanks for the help

Alan K · Jun 2, 2014

I believe they are a 6V system, positive ground. If you post this on the MM forum someone will have an idea where to get a good wiring harness for it.

Steve@Advance · Jun 2, 2014

There should be some clues as to what it is now, chances are it may have been converted to 12v at some time.

Look at the tag on the generator, look for numbers on the regulator, look at the lamps, should be able to find a voltage reference or part number you can cross. Most all 6v were positive ground. If it has battery ignition, look at the coil. If the -terminal is wired to the ignition switch, it was positive ground.

Obviously if it has an alternator, it had been converted, 12v negative ground.

rvirgil_KS · Jun 2, 2014

It was born 6 volt, positive ground. Could have been changed. Steve has covered things to check to see which it is now.

As for wiring harness, if it were mine I would get some good quality automotive wire and connectors and make my own. Just replace wires one at a time. Black split loom works to encase multiple wires. 10 gauge wire from generator/alternator to ammeter and to big battery wire at the starter switch. Rest can be 14 gauge. Tractor and electrons don't care what color wire you use.

If either generator or regulator is bad, for a working tractor it will be cheaper and more dependable in the long run to convert to 12 volt with alternator. Get a 3 wire Delco alternator for a late 70 early 80's vintage GM vehicle

Distributor points and condenser,and original starter will work on 6 or 12 volt, positive or negative ground. Starter turns same way either polarity.

Larry Metzgar · Jun 3, 2014

It appears the tractor has a magnito, so the coil is internal. I was told at this time to change the system over to 12 volt negative ground and replace the existing generator with a one wire alternator. Any place special or brand I should buy. I take it I might have to fab a new bracket and make sure the old pulley and new one are close to the same. Any suggestions? Since the wiring harness are so expensive and so many wirer are eliminated I will just wire it myself making sure I use a 10 guage wire to the alternator from the ammeter and to the starter. I have a NAPA store, advance and Rilleys in town. Thanks Larry

MM R wiring/ battery

Larry Metzgar

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Alan K

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Steve@Advance

Well-known Member

rvirgil_KS

Well-known Member

Larry Metzgar

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