Generator Test - Is it OK?

[MarkN72]

Hi All,

Tested the generator by running as a motor with battery (12v to D+, GND to both GND screw and DF). Seems to spin fine. (Would not spin without DF connected to GND.)

Ran as a motor for about 5 minutes.

Replaced battery with a voltmeter, spun the motor with a drill on fast speed and got about 6V from D+ to GND.

Does this seem OK? Someone said voltage may be low if generator becomes polarized and running longer as a motor may de-polarize.

(Generator was working on car and was disassembled for bearings and brushes.)

Thanks!

[heimlich]

Look this over: http://www.vw-resource.com/generator.html
_________________
www.vwnos.com [email protected]
Classic Brands. Classic Quality.
Not all parts are made the same. NOS OE/OEM parts made mainly in West Germany, Early Germany, and Early Brazil are where VW produced the best quality parts and best fitting products.
5% Off your order with coupon code: 5%OFF
Restored Distributors Available (<--Click here)

[mukluk]

You only need to "motor" the generator for at most a couple seconds to properly polarise it. Motoring it for five minutes is quite excessive and there's no good reason to do so. A generator needs to be polarised so that it retains some magnetism -- this magnetism is what allows it to produce electricity. A generator that is de-polarised or has lost its polarisation will not produce power, at which point you must perform the "motor" procedure to repolarise it.

Spinning the generator with a drill isn't likely to produce enough rpms to test the generator's output, though seeing it kick out 6v should indicate that it is at least working.
_________________
1960 Ragtop w/Semaphores "Inga"

[baldessariclan]

Generator output should be around 12 volts at the “cut-in” speed (i.e. ~790 rpm engine speed = ~1,500 rpm generator speed), and 36 volts at double those rpm’s, per shop manual excerpts below. Also note to keep unregulated voltage testing time short.

_________________
1971 Standard Beetle — fairly stock / driver

baldessariclan -- often in error, never in doubt...

[MarkN72]

Thanks Guys!

I know now that running as a motor for 5 minutes is way excessive for depolarization.

And spinning the generator to check output should be done for a short time only.

Cheers

[Cusser]

[busdaddy]