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914World.com _ 914World Garage _ HEATER FAN QUESTION

Posted by: Michael J Feb 24 2005, 09:12 PM

I am not an electrician so bear with me. If I put an ohm meter on an electric motor and get a reading does this mean the motor is OK?
Seems to me that it shows a completed circut.
Thanks.

Posted by: scott thacher Feb 24 2005, 09:14 PM

for the most part yes the ohms should be very low when the motor is not turning, try hooking up to it again and spining it by hand the ohms should go up and down

Posted by: 914GT Feb 24 2005, 10:12 PM

Ohmmeter measurement is not always an indication of a good motor. A motor can have one or more shorted windings which makes it run hot, have less power, and draw more current. On a brush motor, you can have a dead winding or burned commutator. It'll be an open circuit in one position of the rotor. On an induction motor, you can have a bad startup cap or other bad parts.

Posted by: dmenche914 Feb 24 2005, 10:27 PM

Assuming your ohm meter also can read volts, first start off by making sure the motor is getting the 12 volts when it is supposed to be opening. If no 12 volts then the problem is upstream of the motor, maybe relay, fuse, switch a wire etc... If you got the 12 volts to the motor, then the motor has a problem. You might be able to repair it, or just replace with a used unit.

At anyrate, make sure you are getting 12 volts during the opening operation. If only one side is out of comission, test the good side to see what a good reading of 12 volts is like. You'll want to cycle thru the opening cycle to see if the 12 volts shows up on the motor connector.


PS you are right, zero or close to zero ohms means a good contact, low resistance. resistance is to electricity as a flow restrictor is to a water pipe. Voltage is to electricity as water pressure in a hose. Finally Amps, or current is the amount of flow of electricity, as gallons per hour of flow is to a water pipe.

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