Generator Field Ground

[Dan Partain]

I'm rebuilding a spare generator and am looking for a good way to attach the field ground to the case under terminal assy, but of course keep it separate from the terminal connection. The field coil wire is just long enough to reach that area.

It must have been connected that way before since there are no other holes in the case for a ground screw. I don't really want to drill another hole for a small ground screw if I don't have to.

Seems like I've seen another small plate that goes under the terminal assy against the case for the field ground wire, but there is nothing in the catalogs that I can find.

[Herb Concord Ca]

When I rebuilt 2 generators a few years ago, I drilled hole for a #8 machine screw.
My field ground wires were longer than the one in your picture, so the hole was drilled a quarter turn away from your view.

[Tom Wesenberg]

You show the terminal for the adjustable brush, but the other end of the field coils should have a large eyelet that fits under the output stud and insulating washers. Parts houses sell the stud and insulating washers kit.


Bert's # A-10104

[Dan Partain]

Tom, one of these is the field coil wire for the ground, I thought it was the short one. Here's another photo.

I have plenty of studs and insulating washers. Your words "large eyelet that fits under the output stud and insulating washers." I think that is the part I need, the "large eyelet." I don't see that as part of any kit or separately. That would be the ground connection part that fits against the generator case for a ground under the terminal stud, but still insulated from the output terminal.

I saw a photo of one somewhere, but can't seem to find it, I may have one somewhere but can't find it either.

[Dan Partain]

I found the photo of the part and I also found the part in my generator parts pile, it was connected to a burned up field coil. This is the part that must not be available as repro, I don't see it in any of the catalogs I have. I'm thinking this is the part Tom referred to as having a "large eyelet." This is the part I had remembered and was trying to describe.

Anyway, for future, it looks like it would be easy enough to make one out of some shim stock.

In looking at this generator I have I'm guessing the long ground wire was connected to a screw on the end plate with the brushes as there is no other place it could have been connected. I'm going to use this little connector with a new insulating washer and save drilling an extra hole in this case.

Thanks for the replies.

[katy]

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Weren't some of them connected to the grounded brush holder?

[Dan Partain]

Yes, and here's a summary of what I found.

Model A Ford Generator Field Coil Grounding

I was able to take apart about 8 old Model A generators and various other incomplete units today in my quest for an answer to the field coil ground wire location and method. I thought this may be interesting for others.

There are 2 field coils Screwed into the generator case and wired to each other inside the case. The field coil that has the ground lead will be the one on the same side as the notch in the generator case that locates the rear end plate.

When grounding the generator field coils you have 3 choices for the ground location, and it depends somewhat on the leads coming off of your field coils. Of course you can always make these leads longer or shorter according to your needs.

1. Some generator cases have a small hole specifically drilled to connect the ground wire from the field coil, or you can drill one for that purpose. If I was going to do it this way I would drill a hole for an 8/32" flathead screw and countersink the case for the head on the outside of the case. Then attach the field coil lead with a nut and lockwasher on the inside of the case.

2. Some field coils use a special connector that is soldered onto the wire for grounding to the case as part of the output terminal lead assembly. This connector holds a round insulated washer and serves to isolate the ground connector from the terminal stud.

3. Some field coils have a ground lead that is long enough to attach to the end plate with the brushes. With a small flag type terminal connector it can connect to one of the screws that holds the spring for the rotating brush holder, or the screw for the ground brush. This seems like the least desirable option since the routing of the wire puts it in areas of moving parts.

I drilled a hole for the ground wire as in #1 above, here's a couple of photos. I'm going to remove the flag terminal and shorten the wire and add some heat shrink to the uncovered wires.

[Tom Wesenberg]

That flag terminal is the field feed wire and is attached to the adjustable brush.

Ford never grounded the fields on the end plate.