Generator Test off Car

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Generator Test off Car

Postby HAN5L778 » Tue Mar 24, 2009 12:59 pm

Is there any way to test a generator that is off the car? I found a tach drive generator lying around in my garage and have cleaned it, painted it, and installed brushes. I now want to test it to see if it's any good so I can put it up for sale. I don't like selling things if I can't tell if it works or not. I was told there are instructions in the shop manual for testing, but all I found was testing on a running car.
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Re: Generator Test off Car

Postby jjkuzman » Tue Mar 24, 2009 1:56 pm

Rick -

It has been a long time since I last tested a generator off the car, but if I remember correctly there are at least two ways of testing. The first way is to make the generator think it is a motor. To do this, secure the generator in a vise or by some other means. Connect a jumper between both terminals. Now, using jumper cables, connect a car battery + to the jumpered terminals and - to the generator case. The generator should turn if all is well. The second way is to connect the - battery to the case and first polarize the generator by quickly flashing the battery + to the field terminal. Once polarized, connect a jumper between both terminals of the generator. Connect a voltmeter + lead to the jumpered terminals and negative to the case. I use my impact wrench to spin the generator. As it gains speed, you should see the generator start putting out around 15-25 volts between 800 and 1000 rpm.
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