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Old 09-13-2010, 09:46 AM   #1
Dan Ewing
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Default Generator wiring

After rebuilding my 31 generator , I need a bit of help confirming the wiring hook-up. Here is the way I have it currently wired:

a) the adjustable (3rd) brush is connected to one of the field wires
b) the other end of the field winding (from the second field) is connected to the generator case, ground
c) the ground brush is connected to the generator end plate, ground
d) the output, or armature brush, is connected to the cutout.

Does it make any difference which field coil is connected to the 3rd brush and which one goes to ground? My thinking here has to do with the clockwise rotation (viewed from the pulley end) of the armature.

Here is the story:
My generator showed no charge on occasion but then would sometimes show a charge. I pulled the generator and disassembled. I found the armature brush wire to have a bare spot and assumed that it was the culprit and was intermittently grounding.
I installed a new wire, cleaned the generator, replaced the front bearing and reassembled. I re-installed and now I have the generator running consistently - it does not charge at all. And, yes, I checked the ammeter by turning on the lights and noticing a discharge reading.
I checked the field coils, from one lead through the second coil and out the fourth lead and get a continuous reading. I have not checked the armature. I have checked the brushes for contact against the commutator. With the generator on the car and running, I have checked for voltage at the input to the cutout (generator side) and get a zero reading.
My primary question is the wiring from the field coils as noted in the beginning. Any additional thought s are welcomed.
Thanks for your help,
Dan
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Old 09-13-2010, 09:59 AM   #2
LeroyM
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Default Re: Generator wiring

Snyder's has a good diagram of the wiring and all the parts of the generator in the catalog if you happen to have one. The generator needs to turn the same way the motor turns which is clockwise if looking from the front of the car. Did you polarize the generator? You will need to do this before it will charge. With the lights on at idle the ammeter should show a discharge, when you come off idle and start to increase the rpm's your ammeter hand should come on over to 0 or a slight charge.
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Old 09-14-2010, 08:58 PM   #3
daviscf
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Default Re: Generator wiring

I miswired a new set of field coils by attaching one end to ground and the other to the third brush. No output. Then I checked a diagram showing the field connected to the output terminal & third brish, and 'vola', it works.
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Old 09-15-2010, 07:46 AM   #4
Dan Ewing
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Default Re: Generator wiring

daviscf - interesting how you have your wiring hooked up. Looking in the the Generator Book by Mcree for an internally grounded generator, the internal hook-up is described this way:

> one of the main brushes is grounded to the case via the end plate
> one end of the two field coils is tied to the 3rd brush
> the other end of the two field coils is grounded to the case
> the remining main brush is the output and ties to the input side of the cutout.

I can understand your hook-up to a point and would like to try doing the same except for the remaining main brush. What I hear is this - keep the 3rd brush tied to one end of the field coil; tie the other end of the field coil to the output (cutout) and not to ground. With this hook-up, where does the other main brush tie to if not to ground? If this is the case, this grounds both main brushes which does not seem correct.

Nevertheless, you are getting output with your hook-up.
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Old 09-15-2010, 07:53 AM   #5
Tom Wesenberg
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Default Re: Generator wiring

"Does it make any difference which field coil is connected to the 3rd brush and which one goes to ground? "

Yes, it makes a difference. Keep the correct end of the windings the ground.
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Old 09-15-2010, 09:16 AM   #6
Patrick L.
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Default Re: Generator wiring

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Will the generator motor?? If it does, then you may just need to polarize it.. Polarizing is required when the coils have been removed..
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Old 09-15-2010, 11:11 AM   #7
Dan Ewing
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Default Re: Generator wiring

Tom - I assumed that there must be a difference as to which end of the field windings you connect to the 3rd brush as I also assumed that it is related to the direction of armature rotation.

Could you tell me how to identify which field lead you tie to the 3rd brush? By default, the remaining lead must be grounded I assume.
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Old 09-15-2010, 01:14 PM   #8
Tom Wesenberg
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Default Re: Generator wiring





The first picture shows the current draw on 6 volts for a good field winding.

The second picture shows polarity of the fields.

The third picture shows how residual magnetism will still make the north needle of a compass point to the left field when the brush end is UP and the terminal is AWAY from you.

If you hold the compass on the outside of the case the south end of the needle should be pointing to the left field. Remember you have a coil of wire wound a certain direction and current passing a certain direction to make the left coil NORTH on the inside, so the other end of that coil would be SOUTH.

If there is any doubt, which there obviously is, or you wouldn't be asking, just pick up a cheap compass and try this check.
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Old 09-16-2010, 05:46 AM   #9
Dan Ewing
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Default Re: Generator wiring

Tom - you went through a bit of trouble with your pictured description and it is very much appreciated.

I have a much better understanding of the principle of operation. When the theory (principle) of anything is understood, it makes repair/troubleshooting very easy.

I think you helped me take the training wheels off in terms of my generator opertion understanding. I believe that I should be able to take it from here and get it wired up properly.

I'll try to post a follow up on my efforts from this point.

I would like to thank you again for your kind patience and helping hand.

Dan
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Old 09-16-2010, 06:27 AM   #10
Tom Wesenberg
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Default Re: Generator wiring

Dan,
You're welcome. The reason I like to use a battery charger to check the field is the twisted connection of the two fields, (as seen in the bottom of the second picture), might be a poor connection, and could show 1.25 ohms resistence through the two windings, but a poor connection isn't likely to carry the full 4 amps at 6 volts.

That connection should be twisted and soldered, not just twisted together.
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