In the past, we have talking about check conventional parts of a electrc motor. Here we'll give you some suggestions of other potential problems in checking the motor.
Check the start or run capacitor used for starting or running some motors, if equipped. Most capacitors are protected from damage by a metal cover on the exterior of the motor. The cover must be removed to access the capacitor for inspection and testing. A visual inspection might indicate oil leaking from the container, bulges in the container, or any holes in the container, burnt smell or smoke residue — all potential problems.
Electrically checking a capacitor can be done with the ohm meter. Placing the test probes on the capacitor terminals, the resistance should start low, and gradually increase as the small voltage supplied by the meter's battery gradually charges the capacitor. If it stays shorted or does not rise, there is probably an issue with the capacitor and may need to be replaced. The capacitor will have to be allowed 10 or more minutes to discharge before attempting this test again.
Check the rear bell housing of the motor. Some motors have centrifugal switches used to switch the start / run capacitor (or other windings) "in" and "out" of the circuit at a specific RPM. Check the switch contacts are not welded closed or are contaminated with dirt and grease that could prevent a good connection. Use a screwdriver to see if the switch mechanism and any spring can be operated freely.
Check the fan. A "TEFC" type motor is a "Totally Enclosed, Fan Cooled" type. The fan blades are behind metal guard on the back of the motor. Make sure it is securely fastened to the frame and is not clogged with dirt and other debris. The openings in the rear metal guard need to have full and free air movement; otherwise, the motor will overheat and eventually fail.
Choose the right motor for the conditions in which it will be run. Check that drip-proof motors are exposed to directed water spray or moisture, and that open motors aren't exposed to any water or moisture at all.
Drip-proof motors can be installed in damp or wet locations, so long as they are installed in such a way that water (and other liquids) can not enter due to gravity and must not be subjected to a stream of water (or other liquids) directed at or in it.
Open motors are, as the name implies, completely open. The ends of the motor have rather large openings and the windings in the stator windings are plainly visible. These motors should not have these openings blocked or restricted and should not be installed in wet, dirty or dusty areas.
TEFC motors on the other hand, can be used in all the previously mentioned areas but must not be submerged unless designed specifically for the purpose.
