How To Test The Capacitors On An HVAC With A Stalling Compressor

An air conditioning compressor requires a steady stream of electricity to keep the motor running. If the electrical current should interrupt somehow, the compressor will shut off prematurely, and your system won't receive the necessary refrigerant fuel that provides the cooling. When a compressor suddenly stops working, the problem might trace back to the capacitors.

HVAC units usually have a run capacitor that can give the operating compressor a small boost if the electricity lags. But some units also have a start capacitor that helps the compressor get going in the first place. Consult the owner's manual for your furnace to determine whether you have both compressors. If you do, the testing process for both operates in a similar way. Don't own a multimeter or feel comfortable working around electricity? Call an air conditioning services company.

What You Need:

•    Owner's manual

•    Regular screwdriver

•    Insulated screwdriver

•    Multimeter with AC and Ohms settings

Step 1: Locate and Prep the Capacitors

Turn off the power supply to your unit at the fuse box or circuit breaker. Locate the access panel above the compressor using your owner's manual as a guide. Use a screwdriver to loosen the fasteners on the panel. Lift up on the panel door to remove and set the door aside with the fasteners.

Note that both capacitors will still have electricity stored inside even with the power turned off to the unit so use caution until after you drain the capacitors.

Locate the run capacitor first and carefully remove the wires plugged into the terminals. Lay the end of an insulated screwdriver across both empty terminals for several long moments. Test to make sure the power is gone by carefully hooking up the ends of your multimeter to the terminals, turning the settings to AC, and making sure the reading states zero.

Move on to draining the start capacitor, if relevant. Remove the wires and hook up the multimeter probes to the terminals. Keep the settings on AC and turn the meter on. Watch until the number drops to zero.

Step 2: Test Each Capacitor

You can now test the capacitors for functionality. Before you use the meter, look at the side of each capacitor and make a note of the recommended Ohms range for each. A good capacitor will deliver reading within that range; if the number is lower or higher or jumps all over the place, you will want to replace the capacitor.

Test both capacitors the same way, starting with the run capacitor first. Hook the ends of the multimeter probes to the terminals then turn the settings to Ohms. Check the reading and make your determinations based on the range. Repeat the process with the start capacitor.

If you do need a new capacitor, call an HVAC repair company to come in and install the part. An installation mistake on your part could cause even more problems and leave you with a nonfunctional air conditioning system. Contact a company like Always Ready Repair to learn more.