For most electric motors, you can set the DCV to 20. For an ohmmeter, use the “Resistance or Ohms” setting. When you turn the tool on, make sure the numbers are set to 0. If the display doesn’t read 0, touch the probes against each other to 0 it out. If yours is a digital multimeter, it will automatically 0 out on its own.
Locate a ground screw (often a green, hex head type) or any metal part of the frame (scrape away paint if needed to make good contact with metal) and press a test probe to this spot and the other test probe to each of the motor leads, one at a time. Find the positive (red) and negative (black) wires. Connect 1 probe from your tool to each of the wires.
If the numbers do not move at all, it likely means that your electric motor has an electrical problem. Keep reading to diagnose what might be wrong. It depends on the type of motor you’re testing, but most motors will have little resistance. [4] X Expert Source Duston MaynesAutomotive Repair Specialist Expert Interview. 11 June 2021.
Expect to see a very low value of resistance in ohms. Low, single digit resistance values are expected. Make sure your hands are not touching the metal probe tips, as doing so will cause the reading to be inaccurate. Values greater than this indicate a potential problem and values significantly greater than this indicate the winding has failed opened. A motor with high resistance will not run - or not run with speed control (as is the case when a 3-phase motor winding opens while running).
There are several types of bearings used. 2 popular types are brass sleeve bearings and steel ball bearings. Many have fittings for lubrication while others are permanently lubricated or “maintenance free. "
If the bearings are not spinning freely, try lubricating them. They may be gummed up and unable to spin.
Lubricate the bearings if they are stuck or jammed.
Or, check the capacitor electrically with an ohmmeter. Place the test probes on the capacitor terminals, then make sure the resistance starts low and gradually increases. If it stays shorted or does not rise, there is probably an issue with the capacitor and may need to be replaced.
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.
Broken mounting holes or feet Darkened paint in the middle of the motor (indicating excessive heat) Evidence of dirt and other foreign matter having been pulled into the motor windings through openings in the housing
