How to test Capacitor on your Air Conditioner Unit


After the power is turned off, the HVACR capacitor will be examined. This can happen when using multimeters set to F or MDF. At the end of the idle motor’s cycle, the bulk of the voltage drain will be ejected from the capacitor. When the electricity is switched off, the capacitor runs, and the motor spins when the voltage is turned off. The capacitor will retain an input voltage until an end resistor is permanently connected to it.

how to test capacitor on air conditioner

How to Diagnose and Repair an AC Capacitor

This capacitor testing tutorial will show you how to determine if a running capacitor needs to be replaced. Although the parts are reasonably priced, hiring a maintenance specialist to diagnose and replace them would cost more than $100. You can keep that money if you follow our instructions.

What is a capacitor?

A capacitor is a type of electrical device that holds a charge. They are found in HVAC systems on fan motors and compressors. They are electrically rated in two ways. The first rating is the capacitance of the unit, which is measured in micro-farads (mfd). This is the quantity of charge that the device can store when a specific voltage is applied. The second rating is a voltage rating, which specifies the supply voltage for which the item is rated. In HVAC systems, this is often 370 or 440 volts. This is critical because the capacitor will fail prematurely if a considerably larger voltage is supplied.

Capacitor varieties

There are two types of capacitors used in HVAC systems. The first is a run capacitor found in furnaces, air conditioners, and heat pumps. These capacitors are employed in the operation of fan motors and compressors. They provide these motors with a reasonably steady voltage and enhance their torque during startup. The second type is referred to as a start capacitor. They are found in a variety of air conditioners and heat pumps. They offer additional torque to the compressor at startup. After the compressor begins, a potential relay immediately disconnects them from the compressor. There are two types of capacitors used in HVAC systems. The first is a run capacitor found in furnaces, air conditioners, and heat pumps. These capacitors are employed in the operation of fan motors and compressors. They provide these motors with a reasonably steady voltage and enhance their torque during startup. The second type is referred to as a start capacitor. They are found in a variety of air conditioners and heat pumps. They offer additional torque to the compressor at startup. After the compressor begins, a potential relay immediately disconnects them from the compressor.

Capacitor Examination

A multimeter is necessary for capacitor testing. The capacitance may be adjusted on some digital meters. The power supply should be turned off first, and then the two capacitor terminals should be shorted together with a screwdriver. This will discharge the device, preventing you from receiving a shock. Disconnect the capacitor’s cables. The meter’s leads are then connected to the terminals, acquiring a reading. The reading you obtain should be within 6% of the capacitor’s rating. If your reading is more than 6% lower than the rating, you should replace the capacitor. If you have an analog meter, check the capacitor with the meter set to measure resistance. Please turn off the power, discharge the capacitor, and unplug the connected wires. Then, with the meter set to the greatest resistance, connect the leads to the capacitor terminals. The resistance reading should begin at zero and increase to its maximum value. Bulging of the unit or spilling an oily liquid are both obvious symptoms that the capacitor is failing.

** NOTE** Only you can judge your capacity to complete this challenge. This is only a guide and cannot cover every possible scenario.

Changing a defective capacitor

Look for the ratings on the current part to select the correct replacement part. You should be able to locate a voltage rating (either 370 or 440) and a micro-farad rating. The replacement method is straightforward after your capacitor testing has revealed that you have a damaged component. If you have a dual-run capacitor (a capacitor with three terminals), label the wires and write down where they go. Then unplug the cables, replace the broken component, and rejoin the connections.

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