Rebuilt generator, major discharge

Desert Toad

Desert Toad

Member
I just had my generator rebuilt, including new bearings and having the armatures rewound. This is a shop I've dealt with for years, so I never doubt their work.

When I put the generator back on, the ammeter pegged to discharge and puffed smoke. Do I need to excite this generator so it knows what way it should be making power? Did my shop mess something up?

Thanks.
 
Had to borrow the neighbors internet, found the answer I was looking for here on the forums. Just needed to polarize my new unit - all is well.

Now if I just knew how to delete this post.....
 
Nice to see you got the problem cured!

Regarding the deletion of posts, the FAQ section mentions that there should be an EDIT box on your postings which should allow you to edit or delete the post of your choice.
 
I've worked on 2 generators that customers brought to me that didn't work after the generator shop "fixed them". They fixed one for good :mad:, and luckily the second one hadn't been installed yet.

Make sure the screws holding the cutout to the generator aren't too ong, and make sure the screws on the cutout terminals aren't too long and shorting to the windings.

You should be able to connect a battery to the cutout case and output terminal, and nothing should happen. Now, connect it to the cutout input terminal and case and the contacts should click closed.

Connect a battery to the generator case and output stud and the generator should motor in the same dirrection it normally spins. Do these checks and report back.
 
If smoke was coming from or near the ammeter, it could be from a poor connection at or in the ammeter, or a short from the poor fitting paper insulator in an aftermarket ammeter. I strongly suggest that you check the condition of the wiring and connections on the components on the back side of your instrument panel and the components themselves and the wiring from there to the junction block. Without a fuse, a short will burn up at least one wire and likely cause a fire. An "open" at or in the ammeter could burn up another generator.
 
Ugh. I am still in need of help. It seems this generator is on steroids. I've had this same shop do a lot of work, so I'm tending to think some connections in the car. My daughter was so very excited to put "Frank" in the car show tomorrow, I'm at a loss for what to check next.

The good: The generator seems to work great at all speeds, the needle doesn't shake all over the place like it used to. I can even turn the lights on now without killing the motor.

The bad: As I increase engine speed, the ammeter goes right on up as well. So far up, that about the time it hits 16 amps, my 30 amp fuse in my battery circuit blows.

The cutout out seems to be working correctly and I checked the battery on a load tester.

I'm thinking there must be a bad wire somewhere or at least a bad connection. Any ideas?
 
Reading through my Les Andrews bible, it seems I should be able to adjust the charging rate. But all my brushes are spring loaded.
 

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You have a cheap repro cutout, which ISN'T the immediate problem, but keep an eye on the contacts, as I've seen them get hot and the metal plate burn blue or even black.

You have a Model B generator with two wires coming through a rubber grommet in the case. One wire is the field ground wire and should be screwed to the cutout mounting screw. The other wire is the output wire and gets screwed to the cutout input as pictured. Make sure the wire screwed to the cutout input is the wire that goes to the fixed brush. The adjustable brush is connected to the field wire. You should be able to push and pull the output wire and see where it leads inside the case. It must lead to the fixed brush.

I'm guessing the two wires are mixed up.
 
I thought it was a B generator also but I only see one wire, maybe they grounded it internally or instead of a stud they ran a wire. :confused::eek:
 
Ugh.

I have one wire, like Bob said. It goes to the top most set of brushes, which appears to be the adjustable one. The wire to the lower brush seems to come from an internally grounded wire, kudos to Bob again.

The generator gets hot, wires at the terminal get hot, is there a way I can fix this other than ordering a correct generator? What happened during the rebuild to cause this? I called the shop and the guy keeps saying I have a short somewhere, bring the car in. I didn't have a short before the rebuild.....

Seems like my A might be out of commission for tomorrow show.
 
Keep in mind it the generator was polarize neg ground (most test benches are set up this way) and you put it in the car you will have 12v flowing thru the cut out. Ouch.
 
This should be a quick easy fix if it's the wires mixed up. The adjustable brush is about half way between the ground brush and the output brush. Make sure the wire on the adjustable brush goes to the field winding. The other end of the field windings must be grounded inside the case then.

If you lift the adjustable brush off the commutator and connect a 6 volt battery charger to it and the case, you should have about a 4 amp draw. If you do, then you know it's connected to the field and the field windings are OK.

Any time you work on the generator, it's good practive to polarize it to be sure it's correct. Just jump across the two cutout terminals for 1 second and you're good to go.
 
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Looks like all the brushes are hooked up correctly. Can I move the adjustable one to fix the problem, or is the generator just putting out too much voltage?

And I thought replacing the points was difficult.....
 
Looks like the output brush is putting out 12 volts, the adjustable brush 6 volts. I get a little lost on the electrical side of things, hope I'm using the correct terms.
 
The adjustable brush is mounted on a holder that can be rotated. when the third brush is pushed all the way down, this causes the generator to charge at maximum rate. pulling up all the way on the adjustable brush assembly decreases the charge rate.If moveing the third brush doesn't make any difference in chargeing then the brush wires are reversed and will burn out the field coils if allowed to operate long. When you say that all of the brushes are spring loaded makes me wonder if you understand how the third brush is adjusted. The brushes are all spring loaded but that has nothing to do with the adjustment.

If you have a new Brattons catalog, there is an exploded diagram of the generatoron page 66. the diagram shows the third brush rotating holder an should give you the idea, you just rotate the holder to adjust the brush. There is also internal wiring info at the left lower corner of the page. Brattons catalog has some of the best info available and all model A need one just for the good info, if nothing else. I suspect that you could also have problems with the ammeter. If it has been chargeing for an extended time at 20 amps, the ammeter will get hot and the posts will become loose. I would check the ammeter for loose connections and posts. Hopefully you've got a spare. Good luck and keep us posted.
 
Seems my main confusion is having a Model B generator. It looks like the top brush would be adjustable.

I checked all connections on my ammeter, they are good. But it is quite possible the meter itself has been damaged. But regardless of the meter, I'm still over charging if a 30 amp fuse is blowing.

Are my voltages correct?
 
I don't know about the voltage. Its the amperage output that counts. I rebuild my own generators. The model A,B and model 46 generators all have the same basic adjustable brush set up. If tyour generator has an aluminum end brush plate with vent holes , you have the model 46 generator that was used on the 1933 and later B type engines and was sold as a replacement for the model A generator. The model A generator had an internal ground. the model 46 generator had two wires and one of the wires grounded externally under one of the legs of the cutout. Its common to find these generators with mixed and matched model A parts. I build mine with a post and internal ground but they work equally well either way. If adjusting the third brush doesn't change the rate of charge shown on the ammeter, the brush wires are reversed. I wouldn't worry about the voltage. These generators are very robust and will charge over 12 volts. Check your battery connections. a loose or poor cable connection will cause a voltage spike.
 
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