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Old 03-21-2011, 09:41 AM   #1
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Default Testing a 120v fan motor

I have an Actic Fan with a single phase 120v motor. It has not been used for some time. I read 9 ohms when tested across the elect. source wires, ie, black and white. Does this indicate a fault in the motor windings? Is there another way to test this simple motor other than energizing it and possibly blowing a breaker? When I am doing this ohms test, the feed wires to the motor are connected to the Motor only. I have disconected them at the junction box. Thanks for any help.

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Old 03-21-2011, 10:47 AM   #2
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I have an Actic Fan with a single phase 120v motor. It has not been used for some time. I read 9 ohms when tested across the elect. source wires, ie, black and white. Does this indicate a fault in the motor windings? Is there another way to test this simple motor other than energizing it and possibly blowing a breaker? When I am doing this ohms test, the feed wires to the motor are connected to the Motor only. I have disconected them at the junction box. Thanks for any help.
All that tells you is that the windings are not open. You can't tell anything really useful about a motor's condition from a 9V battery. If you are really worried, you could take it to a motor shop to be tested first.

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Old 03-21-2011, 05:41 PM   #3
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I have an Actic Fan with a single phase 120v motor. It has not been used for some time. I read 9 ohms when tested across the elect. source wires, ie, black and white. Does this indicate a fault in the motor windings? Is there another way to test this simple motor other than energizing it and possibly blowing a breaker? When I am doing this ohms test, the feed wires to the motor are connected to the Motor only. I have disconected them at the junction box. Thanks for any help.
You can hook up the fan thru a SERIES LAMP if the motor is defective as say drawing excess current , the LAMP will become bright, indicating the defect.If there is no defect the fan blade will rotate.
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Old 03-21-2011, 08:29 PM   #4
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Thanks for both suggestions on the fan motor testing. How do I hook up a SERIES LIGHT to test the motor? Aren't you energizing the fan by doing this type of test? Thanks for the explaination.
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Old 03-21-2011, 08:43 PM   #5
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Thanks for both suggestions on the fan motor testing. (How do I hook up a SERIES LIGHT) to test the motor? Aren't you energizing the fan by doing this type of test? Thanks for the explaination.
IN SERIES
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Old 03-21-2011, 08:46 PM   #6
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Hook it up to 120V. You can wire a cartridge fuse inline with the black if you absolutely have to.

Almost all motors read low ohms, because to the meter, the motor windings look like really long wires. It's probably good, unless there's a bad cap. Even then, if it's a weeny fan, it's shaded pole, with no cap.
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Old 03-21-2011, 09:07 PM   #7
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Thanks Miller, appreciate your help. I will let you know what happens. Just for my information, explain to me a SERIES LAMP and how its used to test things. I remember an older electrician in my area( that has forgot more than I will ever know), whom i think had one on his workshop area. He passed away many years ago. Thanks again for your help
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Old 03-21-2011, 09:50 PM   #8
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A series lamp will be a regular light bulb, usually 100 watts, in one of those rubber sockets with the flexible leads brought out.

To test your fan motor with one, you would connect as follows:

120 vac hot source to black lead on socket;
120 vac neutral source to the white lead on the motor;
the white lead from the socket to the black lead on the motor.

That puts the bulb in series with the motor.

If the motor is good, the bulb will light dim (or not at all) and the motor will run.

If the motor is shorted the bulb will light up full intensity and the motor will not run.
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Old 03-21-2011, 10:53 PM   #9
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Attic fan? Like residential 100 something bucks at HD fan?

I'm not even wasting time testing one of those, power it up, if it doesn't work get another motor.

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