How to Know When a Start Capacitor Is Bad

A start capacitor is an electrical device that is an important part of the motor of many heating and air conditioning appliances. Start capacitors give the motor the extra push needed for it to start running. Having a repairman visit to check your capacitor can be costly. You can pocket this cash by learning how to test a capacitor and determine yourself if it needs to be replaced. This process is simple with the right tools and clear guidelines.


Step 1

Disconnect any power lines connected to the motor to be tested. Remove the two screws on the piece that covers the start capacitor. Touch both metal terminals on the capacitor at the same time with a screwdriver with an insulated handle. This will ensure there is no charge left in the capacitor.

Step 2

Set the analog tester to ohms. Touch the meter's two extensions together. Zero the meter by moving the meter's wheel.

Step 3

Touch the positive extension to the negative capacitor metal terminal and touch the negative extension to the positive terminal. Watch how the meter's pointer reacts. A good capacitor will jump the meter and rest at infinite ohms. A bad capacitor will stay at the opposite side, never producing an infinite reading.

Step 4

Check for physical signs of wear like a bulging or leaking unit and replace as needed.