How to Test the Capacitance of a Motor Capacitor How to Test the Capacitance of a Motor Capacitor

What You'll Need
Capacitance meter, in ohms
Screwdriver set

If your electric motor will not start, testing the motor capacitor will help you find and solve the problem. Follow this process to test the capacitance of your motor capacitor.

Step 1: Disconnect Electric Power Supply

Find the live wires for the electric motor and disconnect them. Find the motor capacitor, usually on top of the motor housing.

Step 2: Check the Capacitor For Leakage and Remove It

If the capacitor is leaking acid, it is no longer working. Replace it with a new one. If the capacitor is intact, short out its 2 electrical leads to eliminate stored electricity, using a screwdriver with a nonconducting handle. Remove the capacitor from the motor housing.

Step 3: Test the Capacitance

Set the ohm resistance reading high, to X100 on the capacitance meter, then connect the capacitor leads to the ohm meter leads. The meter needle should move toward the zero mark, then up to the highest reading.

Step 4: Retest as Needed

If the capacitor readings on the ohm meter are different from those in Step 3, short out the capacitor leads again, and retest. If the capacitor does not show correct resistance readings on the second test, purchase and install a new motor capacitor on your electric motor.

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