Testing an HVAC Capacitor with a Multimeter

A capacitor is a device attached to your HVAC unit. The purpose of the capacitor is to store an electrical charge. The capacitor powers the fan motor and the compressor. When a capacitor is faulty, the HVAC unit might not power on. You can test your capacitor before replacing it using a hand-held device called a multimeter. A multimeter is used to test the voltage of electrical devices. This simple troubleshooting process can save you a service call and money.

Needle-nose pliers
Rubber-handled screwdriver

Instructions

- 1
  Shut off the power supply to the HVAC unit at the circuit breaker. Allow the capacitor to cool before working on the device.
- 2
  Pull the wires connected to the capacitor at the connection point, using a pair of needle-nose pliers. Do not pull on the wire itself to prevent breakage. If the capacitor looks swollen or broken anywhere on the body, replace it; no testing is required.
- 3
  Pull the capacitor out from the unit.
- 4
  Touch the metal part of a rubber-handled screwdriver to each terminal on the capacitor at the same time to discharge the unit. Using a rubber-handled screwdriver prevents shock.
- 5
  Set your multimeter to the RX1 setting.
- 6
  Touch the red probe of the multimeter to the "ohm" terminal on the capacitor, and the black probe to the "com" terminal. The meter should read zero. If it doesn't, the unit is faulty.

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