Generator charging problem update

[Marshall V. Daut]

It just gets "curiouser and curiouser"... This is a follow-up to my previous posting: https://www.fordbarn.com/forum/showthread.php?t=330390

O.K. I finally got some free time, so I spent the last 1 1/2 hours switching generators and cutouts around in an effort to find the cause of the no-charging issue in this rebuilt generator. Briefly, I checked this generator and a known good generator with four cutouts: three Nu-Rex electronic positive ground cutouts (numbered 1-3 for my tests) and one original points cutout (numbered #4). The known good generator showed a charge with all four cutouts, which is the good news. The issue is therefore not cutout related. That's a relief.
I put the generator in question back on the engine and tried all three electronic cutouts. No charge. Putting on #4 original cutout, the ammeter registered a charge. I then took the generator apart, looking for frayed wires or bare wires touching the steel case. Nothing. Re-assembling it, I tried #4 cutout again and the generator charged, as before. But NONE of the electronic cutouts charged, although all three worked on the other generator. Strike three.
Then something curious happened. I took the fan belt off the generator pulley and ran jumper cables from the battery to test for "motoring". The generator motored very well, but it spun in the wrong direction! I removed the cables and hooked them up to the known good generator. Viola! It turned in the correct direction. And then something even more curious happened. I connected the jumper cables to the questionable generator again (still on the engine) to double-check the spin direction. Still the wrong way. But...as I removed the hot lead and momentarily left the ground cable attached to the generator case, the armature continued to motor, albeit slower. What the heck is going on here??? It should not motor at all with only one jumper cable connected, especially the ground jumper cable, not the hot lead.
The package containing the new field coils was clearly marked for a six-volt system and when the generator was tested with my six-volt battery, it turned over rather quickly for a generator compared to a starter. So, I'm confident that the field coils are not 12-volt. Same with the armature. But what would make the armature turn in the wrong direction with all new parts and why would an original cutout produce a charge in this condition, but not the electronic ones? I can only assume that the flow of current is going in the wrong direction to make the electronic cutouts kick in, but the original points cutout doesn't care one way or another.
So, why does this generator motor in the wrong direction? That has got to be the cause of this generator's non-charging issue with electronic cutouts. I am not an electrical guru enough yet to figure this one out on my own and the Model A generator-starter booklet does not give a cause for this in the trouble-shooting section.
Ideas???
Marshall, the Electrically-Challenged One

[Marshall V. Daut]

By the way, the field coils were installed the same way I have installed in previous generators with the connecting wire between them laying on the bottom of the case. The paper insulator is in place and the connecting wire is sheathed, so no shorting out here. If the coils were switched side for side, I believe that would cause the armature to spin in the opposite direction as I am experiencing, right? But the field coils were installed in the correct orientation. I also grounded the wire to the case itself, not to the terminal post.
Marshall

[Bob C]

Didn't Tom W use a compass to check the polarity of the poles?

[Marshall V. Daut]

Because the field coils are oriented properly inside the generator housing, but the armature spins in the wrong direction, I am wondering if the coils were wound backwards, meaning the positive coil is now the negative coil and vise-versa with the other one. Wouldn't that account for the reverse rotation?
Marshall

[1955cj5]

Could the brushes be reversed?

The movable brush goes to the field but how about the other two? One to ground and the other to the output.

I'm about to tackle my generator so am interested in the outcome.

Randy

[Marshall V. Daut]

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The rounded top edges of the brushes are against the brush holders, their correct orientation. I double-checked that.
M.

[1955cj5]

If you reverse the polarity of the jumper cables does motor in the correct direction?

I'll go try my soon to be rebuilt generator( it really only needs bearings) and see what it does, and will let you know.

[1955cj5]

I don't really understand why, but with the black/negative cable from the 12v portable jumper box clipped to the generator case, and the red cable to the output post, the generator motors to the left as viewed from the rear.

With the positive/red cable connected to the case, and the negative cable hooked to the output post, the generator motors to the left also, as viewed from the rear, and at the same apparent speed.

Like starters I guess, built to rotate in one direction only.

[rotorwrench]

The field coil direction of pole shoe windings has to be observed during assembly. One side is a north and the other is a south as far as the field polarity is concerned. It seems to be that they were inadvertently swapped.

If you look at a Ford electrical diagram, a person can look at the direction of rotation of each coil in the set. One is wound clockwise and the other is counterclockwise. A person has a 50/50 chance to of success. It really gets fun on the powerhouse generators with their multiple coils.

Starter motors are shunt wound so they can only turn one way no matter the polarity. A generator is a different story.

[Marshall V. Daut]

Swapping jumper cable connections made no difference in motoring the generator: still reverse rotation.
M.

[nkaminar]

Switch the field winding wires. The wire that is now ground goes to the 3rd brush and the one that now goes to the third brush goes to ground.

There are two ways to switch the direction of a DC motor, one is to switch the armature polarity and the other is to switch the field winding polarity. When you change the polarity of your jumper wires you switch both. It has to be one or the other but not both.

[Marshall V. Daut]

Yes, I had pretty much decided after all my tests, PIA disassemblies and re-assemblies that my new field coils were wound at 4:59 on a Friday afternoon by someone wanting to get the hell out of the factory for the weekend, i.e., wired backwards, as the bare wire SHOULD have been the ground and the sheathed wire should go to the adjustable brush. That' s the way it was with the other five field coils sets I have successfully installed this year. There's no other logical explanation for the armature spinning backwards other than improperly wound field coils with reverse polarities. Or do the field coil shoes retain their polarity, thus "confusing" the field coils if the shoes have been switched from side to side? 'Dunno...
I will switch the two field coil wires around tomorrow, although it's going to be a hassle now that the bare wire was shortened to function as a ground against the generator case. I'll have to re-drill the ground screw hole on another case web and sheath the bare wire, as well as extend it and somehow come up with a flag connector.
Marshall

[jb-ob]

Or "I wonder how long it will take 'em to figure I wired the coils backwards just for spite !"

Or maybe the assembler was trying to make the transition from American electrics back to Lucas ?

[Marshall V. Daut]

Nah! If this had been Lucas, the field coils would have caught on fire and burned up while still in the bag.
M.

[Big hammer]

I’am no expert but can a generator charge positive or negative ground ? Why do some need to be flashed to get the generator to charge. I would try to flash the fields before rewiring the coils.

[1939mars]

Could the residual magnetization in the fields be the wrong way? The link below talks a little about the residual but not how to affect it. I think it is saying there needs to be a little residual in the fields for it to self-start the feedback loop to grow the voltage. Maybe taking a strong magnet to it would force it to flip? You're probably getting sick of taking them apart but it would be interesting to know if the working ones all have the same polarity of residual.

https://circuitglobe.com/characteris...generator.html

-Scott

[1955cj5]

Originally Posted by Bob C

Didn't Tom W use a compass to check the polarity of the poles?

I was intrigued by this comment....Thanks Bob.....

First picture shows magnetic north, more or less....the red half of the needle points North.

Second picture shows generator North, more or less...

Third picture shows generator North, with the generator rotated 180°, more ore less...

Randy

[Marshall V. Daut]

"I would try to flash the fields before rewiring the coils."

I did flash the generator with the points cutout in place. That got the generator charging, but it didn't continue to charge with the electronic cutouts.
M.

[ndnchf]

The fields are nothing but coils of magnet wire. They can't be wired wrong, but can be assembled and formed wrong. That may very well be what happened. You could separate and unwrap the coils to see how each coil is oriented. Unwrap an old set of coils to compare, then rework the new set to match. You'll need re-arch the coils too, but that is easy enough.

You might be able to save the original coils. Often its just the wrapping that is oil soaked and deteriorated. I have rewired and rewrapped many coils over the years. My youtube channel has a 9 part video series on rebuilding a 1940s Autolite generator. In part 7, I discuss rewrapping the coils.

https://youtu.be/iUMOd0FXNDA?si=mBwv5FEHbvDhYYha

[Marshall V. Daut]

Good input, ndnchf. But wouldn't simply switching the two field coil wires around accomplish the same thing and make the coils' polarity correct? As an obviously seasoned electronic wizard, can you think of anything else that would cause the armature to spin in the wrong direction other than the field coils being oriented incorrectly in tandem? I can't.
Marshall