I was going to remove my generator to bench-test the unit and adjust my brushes, do I need to flash it when back on the car? The service manual doesn't say anything about it?
As long as you don't foul up the residual magnetism with another voltage source it shouldn't require flashing.
If the generator had been working properly you should not have to flash it. If you have applied current to the generator in any way while bench testing it you need to flash it to insure the correct polarity.
But then on the other hand it won't hurt a thing to do it. I would.
Okay, I plan to bench test it with a 6V source so it'll probably need to be flashed.
Now, silly question- I haven't done it in years so can someone refresh me and flash my brain as to how to do it?
Which brings up my question. In all my years of working or playing with cars or anything with engines I don't think I ever learned the proper way to flash a generator. Could one of you electrical aficionado's enlighten us in layman terms? Jim
Seems like us Jim's are in the same boat. Jim
If you didn't disturb the poll shoes, it most likely won't need to be flashed. In any case, just apply power (+6v) to the output terminal and ground the yoke. With the third brush raised off the commutator, it should motor. That's all there is to it.
I recently had a Model A generator that would motor, installed it back in the car and would not charge, I took the hot wire off of the side of the regulator and touch it to the main terminal and it started charging? First time that ever happened but maybe that is what flashing is??
That's what flashing is Joe.
To polarize the generator you take a short jumper wire and touch both connections on the cutout at the same time.
Just arc it. Make a spark. A split second is all it takes.
you can also use a pair of pliers to do it.
Just to clarify, make a generic jumper wire, pliers, alligator clips or whatever and connect the main brass screw (positive connection on top of gen) to the screw on the opposite site of the cut-out for a split second?
WARNING! WARNING! DANGER WILL ROBINSON!
"Jumping" across (or around, if you prefer) the cut-out works only if you have an original mechanical cut-out OR a diode style cut-out.
If you have a Fun Projects Electronic Regulator and you jump across it YOU WILL RUIN IT!. Just remove the wire from the front and flash the generator output stud. Went in doubt as to the type of cut-out, always remove the wire and flash with it. Good luck with your project.
Thanks for the caveat.
Truly it is best to completely remove the VR from the generator if you have one on there. That way you can't hurt the VR. Connecting the POSITIVE connection from the battery to the generator stud and the NEGATIVE connection from the battery to the generator case will motor the generator and also polarize it. As others have stated, if you see a spark it has been polarized. Motoring the generator is often the reason that generator gets polarized the wrong way since it will spin regardless of the polarity you apply but if you apply it backwards with Negative to the generator stud then you have just polarized the thing backwards (Positive ground) and that can destroy the VR when you then hook the VR back up to the generator. The Model T VR is expecting a positive voltage at the input connection.
Thankyou John, I just copied your post into a Word document and saved it with my other Model T nuggets of wisdom.
Thanks John I will do this when I get around to putting one of your vr's in my 26. Jim
P.S. It has been sitting on the shelf since 08. Shame on me! Jim
Totally not true John. The third brush MUST be down to polarize the generator. The generator will NOT motor with the third brush down, if the lead is adjusted correctly. I was too abbreviated in my answer and mixed thoughts as the OP stated he was bench testing. And I made the assumption he knew positive from negative.
In your haste to ridicule other's posts, I suspect you forgot that the field coils are what "flash" the generator polarity and are connected in series with the third brush and the negative brush. If the third brush is lifted, there's no connection of field coils for positive and thus no polarization even though you see a "flash" or spark at the positive terminal.
(Message edited by ccwken on August 18, 2015)
I should explain that the reason you will still see a spark at the positive terminal with the third brush lifted is because the positive brush and the negative brush are in contact through the commutator (armature winding).
I did not intend in any way to ridicule anyone or any post. I reread the post and I simply was concerned that attaching the battery wire directly to the generator while the VR is installed is exactly the same issue which can hurt the VR by jumpering the battery side to the input side. I apologize to anyone I offended - I shall withdraw from this thread.
"The generator will NOT motor with the third brush down..."
That has not been my experience.
Finish the quote:
"The generator will NOT motor with the third brush down, if the lead is adjusted correctly."
Apparently, yours is not.
Never mind. You are correct.
Alright, I have a good generator installed back on the car now. To "flash" my generator:
a. remove cut-out from generator
b. touch yellow battery wire to large generator post with nut for a split second
Is that it? Do I have this correctly explained?
James. I think it would be best if you keep your pants on!
ar ar ar!
So what's the story with the 3rd brush? Up or down?
The generator should motor with third brush down and motoring the generator will also polarize it. This is why it is recommended that when motoring the T generator connect the generator brass stud post to a positive voltage and the case of the generator to a negative voltage. If it was polarized backwards before you motor it this way it will have the correct polarity when you are done.