Polarizing Generator on the 69 140?

[Brandon Webb]

What terminals on the voltage regulator do I need to touch together to make a 1969 140 charge? It was charging but dad took the battery out for some reason. I went about 2 rounds raking hay with it and it died. Glad it's not mounted under the hood. Thanks

[Gary Dotson]

Bat. and Gen., just a quick arc.

[AL Farmall Boy]

The middle of the 3 terminals on one side.....and the single terminal on the other. If you have one of those newer type regulators with the single terminal under the regulator, just arc it at the other end of the wire on the generator. I'm sure you know, but I'm going to mention for others that A 1969 is a factory 12 volt, negative ground system.

[w30bob]

Hi Guys,

This is an interesting topic. I was reading up on when you need to polarize the generator the other day and there's a lot of info on here and on Yesterday's about it. From what I summarized you only need to polarize if the battery has been disconnected for a very long time.......like months. It was discussed that the manual mentions the need to polarize every time the battery is disconnected, but the experts in that discussion indicated that was just not the case. They were saying it takes a long time for the magnetic field to wear off. I was buying that explanation, but now reading what Brandon said I'm curious to hear how long Brandon's dad had the battery out.

thanks,
bob

[Slim140]

Our recently purchased 140 had been sitting for 10 years. I installed a new battery and cranked it and it was charging WITHOUT doing anything to the generator. I unhook the battery every time I shut it off because the wiring harness is not in good shape (have a new one, just haven't installed it yet). I hook the battery and crank it and it charges every time.

[w30bob]

Hi Shane,

Thanks. There's definitely evidence out there that the gen doesn't need to be polarized as often as the manuals suggests....as in your case.....and in my case where the 140 I just bought was also sitting for a long time unused with a dead battery. I had the old battery out for over a week, then put a new battery in, and she charges fine. So I guess it doesn't hurt to polarize......and you obviously need to do it if the gen isn't charging......but other than that I guess it gets a little fuzzy as to when it needs to be done.

thanks,
bob

[Jim Becker]

For a generator to charge, there has to be residual magnetism in the field (the frame and field shoes). Polarizing temporarily puts current into the field coils to magnetize the field. The direction the current runs determines the direction of the field magnetism. It needs to be the right way for how the battery is installed. You need to polarize a generator (magnetize the field) whenever:
- the frame isn't magnetized, or
- the frame is magnetized backwards.

All you have to do is polarize it whenever you have either of the above. Anybody want to take a stab at circumstances or actions what could cause either of them?

[Slim140]

Jim, pure guess here. I’ll say if the battery is hooked up backwards or if there is a bad ground between the generator and or voltage regulator connections?

[AL Farmall Boy]

Anybody want to take a stab at circumstances or actions what could cause either of them?

When the battery is unhooked and reconnected (in any fashion) at some point.

[w30bob]

I can only think of two scenarios.....

When you forget your tractor is in gear and you bump the starter......and it starts and drives into the pond you parked it in front of. When you fish it out you hook up the jumper cables backwards because when you replaced the battery and starter cables last week you got a black battery cable and a red starter cable cuz that's all they had at the redneck auto parts store on a Sunday afternoon......and when you tried to jump it you weren't thinking so you saw red and said "positive" and hooked red to red. Plus it was a stinking hot day, you're girlfriend wouldn't stop telling you "I told you so" and you had a few too many beers (but diving into the lake to hook the chain up to the tractor sure felt good).

Don't ask. ;O)

Or......when you rebuild the generator.

regards,
bob

[Dale Finch]

Oh my!!!

[Jim Becker]

OK, here's the way I see it:

- the frame isn't magnetized

Maybe never magnetized -- a new out of the box generator may have never been polarized so no magnetism. Probably depends on what quality checks were done at the factory.

The residual magnetism will decrease over time, how quickly and how completely is an open question. Clearly the longer it sits unused (no field current applied), the more the magnetism will decrease. It isn't going to happen over night. (Obviously, as the battery is unhooked from the generator every time the engine stops.) Not going to happen over a long weekend or other much longer periods either. Maybe it will happen if the generator sits on a shelf for a decade or so.

Maybe somebody could run one through a degausser and kill the residual magnetism.

- the frame is magnetized backwards

For this to happen, a field current needed to have been applied backwards. Lots of ways to do this: battery installed backwards, wires miss-connected one way or another, stray wire contact while doing electrical work, maybe some odd lost ground situation.

Somebody could test a generator by seeing if it motors over when power is applied. Depending on which way they hook it up, they could reverse the polarity. Any generator that goes into a rebuild shop will certainly be hit with a field current. The shop doesn't know or care which way it will be hooked up. Polarity out of the shop is a coin toss.

Those are all the ways I can think of to get in polarity trouble with a generator. Clearly, you shouldn't need to repolarize just because you disconnected or removed and replaced a battery. That is as long as you don't put the battery in backward. But if you do any other work on the electrical system, including removing, repairing, or replacing the generator, polarizing is a good practice. This is a simple rule and probably covers all the scenarios for lost polarity.