# How do you test the resistance of an electric motor?

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## How do you test motor resistance?

Touch the red (positive) lead of the multimeter to the positive end of the wire windings around the motor. Touch the black (negative) lead of the multimeter to the negative end of the wire windings around the motor. The reading that appears on the multimeter screen is the resistance in ohms.

## Can you test an electric motor with a multimeter?

Inspect the Motor Windings With a Multimeter

To begin, set the multimeter to read ohms and then test the motor’s wires and terminal. … To test your motor for short to ground, you’ll need to set the multimeter to ohms and disconnect the motor from its power source. Then inspect each wire and look for infinite readings.

## How do you test an electric motor with an ohmmeter?

Check for shorts between the power wiring and ground. Select ohms resistance on the multi-meter and set for the 30,000-ohm range. Touch one lead to each motor power lead and the other to the metal motor casing. Any value less than about 0.2 mega ohms is a reason to discard the motor.

## How much resistance should a motor have?

With a multimeter, measure the resistance between motor frame (body) and earth. A good motor should read less than 0.5 ohms. Any value greater 0.5 ohms indicate trouble with the motor.

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## Should an electric motor have continuity?

The windings (all three in a three-phase motor) should read low but not zero ohms. … It will usually be low enough (under 30 Ω) for the audible continuity indicator to sound. For proper motor operation, all windings must have megohm readings to ground, i.e. to the motor enclosure.

## How many ohms should a DC motor?

The meter should read a low resistance in the area from 10 to 30 ohms. If the meter reads an infinite ohms reading or an open circuit, rotate the end shaft of the motor.

## What’s the best way to diagnose an ECM motor?

Diagnosing ECM Motors

1. Verify that the correct thermostat input voltage is present at the interface of the main control board on the furnace or air handler. …
2. When checking low-voltage connections, always use the C terminal on the board, never on the ground.

## How do you check the windings of an ECM motor?

Measure winding to winding on the plug feeding the motor (called phase to phase below). Resistances should be less than 20 ohms and nearly the same between all phases/windings. Measure from each winding to ground on the casing, and you should see no less than 100k ohms to ground.