An on topic electrical question!

Bob Bancroft · Sep 10, 2016

Delco 12V 2 brush generator. Polarize it, and it works fine. Try it a little while later, and it still works fine. A few hours or more, and it acts like it's totally lost its residual magnetism- just won't charge. What can be done?

Steve@Advance · Sep 10, 2016

Bet this gets interesting!

I've not heard of this happening. Had old vehicles with generators that could sit for a long time, even with a dead or no battery, and still charge without having to polarize it.

I'm wondering if there might be a regulator problem... Borderline adjustment on the cutout relay? Some regulators are polarity specific, not sure what happens if it's wrong.

Where is the vehicle stored? Is there some type of electrical equipment or process near by that could be confusing the polarity? Might also check the polarity of the battery. If it has been totally discharged, it could be reversed.

Basically just thinking out loud here... I don't know! LOL

J. Schwiebert · Sep 10, 2016

Have you done a "motor test" on just the generator? Is this an A or B circuit generator?

Bob Bancroft · Sep 10, 2016

Approx. 1965 AC series II D15. 1960 Chevy Biscayne. Basically the same generators. Doing the same thing. Stored inside. No other strange electrical things going on. Battery polarity all correct.

Bob Bancroft · Sep 10, 2016

Haven't done motor testing. See two vehicles below. Field and armature terminals, connected to a voltage regulator. Ground the field terminal for full charge.

teddy52food · Sep 10, 2016

Try adding a ground wire from the generator to the regulator.

sotxbill · Sep 10, 2016

Could be bad genny or bad regulator...

everything from a bad armature, shorted field coils, etc..

but the magnetic charge on the soft iron field shoes should stay unless exposed to an alternating or reverse field.

Owen Aaland · Sep 10, 2016

I would expect you to find a poor ground through the regulator.

When you start the engine, and it is not charging check, the voltage between the F terminal and the case of the generator. If it is more than .2 volts you have a problem. Ideally you should have zero volts. If you have voltage short the terminal to the case of the generator. If it then starts to charge you will have confirmed the problem is with the regulator or the field circuit wiring.

Bob · Sep 11, 2016

Ground the field and start is up and see if it charges.

If NOT, there may be a short/leakage in the armature or field coils that bleeds off the small amount of current generated by the residual magnetism in the polepieces at startup.

mj · Sep 11, 2016

(quoted from post at 17:43:07 09/10/16) Approx. 1965 AC series II D15. 1960 Chevy Biscayne. Basically the same generators. Doing the same thing. Stored inside. No other strange electrical things going on. Battery polarity all correct.

Seen any UFOs flying around lately? 8)

An on topic electrical question!

Bob Bancroft

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Steve@Advance

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J. Schwiebert

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Bob Bancroft

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Bob Bancroft

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teddy52food

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sotxbill

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Owen Aaland

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Bob

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mj

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