I think my generator is toast

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Model T Ford Forum: Forum 2017: I think my generator is toast
Top of pagePrevious messageNext messageBottom of page Link to this message  By George Davis-Williams - Lake City, MI on Monday, November 06, 2017 - 09:56 pm:

Hello!

Before I buy a new generator I'd like to pick your brains. So the short version is my generator quit charging. .05ish volts at the post. It has a new this summer 6 volt diode cut out, which is working. It'll run as motor when I put it on the bench (using and old 8 volt battery). The commutator mica was flush with the surface, so I undercut it. Put new brushes on and seated them. Tested on the bench again, rain great as a motor. Reset the neutral and put back on the car. Aaaaand, still 0.5 volts max output. Moved the third brush all over, no change. Used some jumper cables to ground the casing directly to the battery negative post, no change on output.

The armature looks really rough and I'm thinking it is just shorting out internally.

So, new generator time?


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Davis-Williams - Lake City, MI on Monday, November 06, 2017 - 09:59 pm:

Whoops, I wasn't very clear. There is a 6 volt battery in the car and I have an 8 volt battery on the bench.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Monday, November 06, 2017 - 10:13 pm:

Get the armature tested.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A Bartsch on Monday, November 06, 2017 - 10:35 pm:

Ditto Mark's advice. And maybe first check the easy stuff with a VOM, field continuity & shorts, commutator to armature shorts, brushplate/brusholder insulation, esp the 3rd brush, good luck. jb


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dewey, N. California on Tuesday, November 07, 2017 - 01:43 am:

Test the armature on a Growler for internal shorts before tossing it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Willard Revaz on Thursday, November 09, 2017 - 12:54 pm:

Try "flashing" the generator while the engine is running. Jump a wire across the cutout momentarily to energize the field while watching the ammeter. You will get a spark and the meter should peg at full charge. This is an old trick many do not know about but which I Have found to work a good percentage of time, especially since you have done all the right things in the rebuild.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Willard Revaz on Thursday, November 09, 2017 - 01:03 pm:

Try "flashing" the generator by touching a stiff wire across the cutout for a second. It will spark and watch the ammeter for a full charge indication, which will continue at a lower rate when the jumper is removed. This is an old trick many are not aware of, but has worked for me in many cases, especially with a complete rebuild, as you have done.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Davis on Thursday, November 09, 2017 - 01:33 pm:

If You have a old electric motor that You can mount on a board You can build a test jig to spin the generator without putting it back on the car.
Might be a challenge with gear driven generator unless You can pull the gear and install a temporary pulley for testing, or put a matching gear on the motor, Auto Zone has free testing for pulley driven Alt/Gen.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Don A on Thursday, November 09, 2017 - 03:57 pm:

I test generators with my lathe. I place an old cam shaft with timing gear in the chuck (timing gear in the tail stock with live center). I made a bracket (like a big pipe clamp) to hold the generator in the toolpost of the carriage. I then mesh the generator gear with the timing gear. I connect the generator to a battery with an ammeter in-line. Works slick as a whistle.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Fred Dimock, Newfields NH, USA on Thursday, November 09, 2017 - 07:18 pm:

If my generator was toast I would get some grape jelly to go with it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Davis-Williams - Lake City, MI on Friday, November 10, 2017 - 02:34 pm:

Thanks everyone! I did take the generator off again, I checked the new brushes to see how they were seating, may 50% contact, so again, reserved with some sand paper per the MTFCA Electrical manual. Tried to bench test, nothing, won't run like a motor now. I don't have a lathe but I do have and electric motor in the barn, so I will try to rig up a new testing stand. In the meantime I did order a new (used) generator from ebay...simply because weather willing I plan on taking the car to Deer Camp this week. However, in the spirit of learning I plan on continuing to tinker on the old generator. Gotta learn somehow!

Fred, the generator is next to the beer fridge in the garage...maybe I will get toasted tonight too!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Fred Dimock, Newfields NH, USA on Friday, November 10, 2017 - 06:29 pm:

George -

If you become toast - please- I say- please donít cover yourself with grape jelly.
I canít imagine what that would look like!


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Davis-Williams - Lake City, MI on Friday, November 10, 2017 - 07:39 pm:

Oh my gosh, that's good! Bahahahaha


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