How to Repair a Central Air Conditioner Dual Capacitor

air conditioning units outside a building
  • 1-3 hours
  • Intermediate
  • 0-200
What You'll Need
New dual capacitor

It’s very easy and entirely possible to repair a central air conditioner dual capacitor by yourself without calling a qualified repair technician. It might even be faster to get the job done on your own, especially if it’s summertime and you want to escape from the heat of the streets to the freshness of your home.

Step 1 - Open the Air Conditioning Unit

Shut the circuit breaker off in your main electric panel. If you’re not sure which circuit breaker your air conditioner is connected to, shut them all off. There may be more than one breaker involved. Make sure the power is off before working with any air conditioner.

Take the door or cover off of your unit's control box and find the run capacitor. The capacitor will either seem fine or it’ll be damaged, swollen, or blown apart and capacitor oil will be everywhere. If the capacitor seems undamaged, spend more time checking it out by following the steps below.

Step 2 - Discharge the Capacitor

You’ll need to discharge the run capacitor and make it safe for further check up. Discharge the capacitor by using a very well insulated tool such as a screwdriver. These capacitors store a high amount of power, which can give you a nasty shock if not handled properly. While it won't kill you, it will definitely hurt you! Put the screwdriver over the capacitor’s terminals to cut the electricity short and discharge the capacitor.

Step 3 - Check the Capacitor

man working on an AC unit

If you have a dual-rated capacitor, you’ll see three terminals marked Herm (short for “hermetic,” which indicates that the compressor is part of a hermetically sealed system), Fan (may or may not be indicated), and C (common) across the top of it. They are called “dual-rated” capacitors because the capacitor helps run both the fan and the compressor.

You need a multimeter to test the microfarad (MFD) rating. Clip the punches on terminals C and Fan, and check if rating is still within the appropriate limits. Do the same for C and Herm. Appropriate capacitor ratings are noted on the manufacturer label. You should always see a lower value for Fan and a higher value for the compressor.

Step 4 - Replace the Capacitor

When you’ve checked everything out and you’re sure that one or both of the capacitor’s values are not near the appropriate requirements, it’s necessary to change it. There are two critical specifications that need to be identified when looking to replace an air conditioner's dual-run capacitor: the voltage and the capacitance rating in microfarad (MFD), which you checked using the multimeter.

The physical size and shape is irrelevant and you’ll find newer capacitors considerably smaller than older ones of the same rating. You can use an alternative of a higher voltage rating but the capacitance should be within 10 percent of the original. Nevertheless, an exact replacement is always best.