Single wire altenator

pointrow · May 24, 2017

Switching M5 gas to single wire alternator. When I hook up the wire to the battery it shorts out. First one tested bad but the next 2 shorted out just like the first.
Any ideas? Do I need to add a diode? The only thing left is the battery but it starts and runs the tractor just fine.
12 volt neg ground

thanks

pointrtow

mmfan55 · May 24, 2017

I have used several of the single wire alternators and never have used anything between alternator and battery. My guess is your missing or overlooking something. I always hook alternator wire to a "junction block " , (usually battery terminal on starter) not directly to battery post.

pointrow · May 24, 2017

I'm hooking to the batt terminal on starter also. Only thing between is the amp meter and I bypassed that also.
This thing has several people scratching their heads.

thanks

pointrow

molinegb · May 24, 2017

Basics of regulator. In ground and out. Grounds common on battery and alternator?

Roger H MI · May 25, 2017

If you have the battery hooked as neg - grd. There should not be a problem.
Diodes in the alternator would block a melt down from the battery. Most
GM alternators will charge after reaching an effective RPM. If you want to charge at lower
RPM then you will have to excite the stator windings.

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Jon Hagen · May 26, 2017

Sure sounds like your tractor is hooked up pos ground. If you verify that the battery is indeed neg terminal to ground, any chance that the battery was once completely discharged and recharged backwards ? Use a voltmeter to verify that neg post on the battery is indeed electrically neg.

pointrow · May 27, 2017

Thanks Jon. That's what it was. Battery had reversed polarity. Funny how it would still crank and run just fine reversed. Pulled battery and put load check on it and confirmed it was reversed.

thanks

pointrow

John B. · May 27, 2017

The older starters with field windings will rotate the same direction whether or not the battery is hooked up neg or pos ground. So if you reverse the battery cables you will reverse the current flow in the starter armature and the field windings so rotation doesn't change.

In order to reverse the rotation of a starter with field windings you have to reverse the current flow in either the field windings or the armature windings but not both.

Newer starters with permanent magnets for their field will reverse by reversing the battery cables because you're only changing the current flow thru the armature. The field polarity is remaing the same. Those field polarities can't be changed. Never tap on these starters with permanent magnets because you can shatter the magnets ruining the starter.

pointrow · May 27, 2017

That's good to know. It sure has been a learning experience.

thanks

pointrow

Jon Hagen · May 27, 2017

Weird stuff happens on occasion, glad you found it. With that problem fixed, the one wire alternators will work as they should.

Single wire altenator

pointrow

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