Central Air Conditioner Humming Noise Them And How To Fix Them

A C Capacitor are devices used to store electric charge that can be used to start the motor when required. There are three main motors in an air conditioner, i.e., blower motor, compressor motor and outdoor fan motor. Each one of these motors have separate capacitors normally to start them up and keep them running. When no proper cooling is getting done, the culprit can be a starting capacitor.

In some air conditioners, dual run capacitors are used to run motors of the compressor as well as the blower. Dual Run Capacitors may not look much different from the Run Capacitors, but if it is a Dual Run Capacitor, motors of the blower as well as the compressor will fail to start together.

warm air

A C Capacitor How Do You Troubleshoot Them

central air conditioner humming noise

Troubleshooting Capacitors
Caution: It is advisable to be extra careful with the electrical devices, such as an Air Conditioner. To be safe, always wear rubber slippers and use gloves that are made from an insulating material.

- A humming sound near the condensing unit, but no fan rotation is an indicator that the capacitor needs to be replaced. If fan is not rotating and a humming sound is heard, then a gentle push to one of the blades of the fan with a thin wooden stick can set the air conditioner running for a while. It confirms that the capacitor needs to be replaced. This test does not apply for the Dual Run Capacitors, but works most of the time for the Single Run Capacitors perfectly.

- A Multimeter can also be used to check if the capacitor is blown out or not, but it is not necessary if other indicators are clear enough.

Follow These Procedures To Be SAFE !!!

Note: Please turn off the power supply to the Air Conditioner before proceeding any further.

- Be 100% sure that the power supply to the Breaker Panel is turned off.
- Find the start capacitor and look at it carefully. If it looks swollen or has got out of the normal shape, it needs to be replaced.
- Capacitors store power, so even if the main power supply is turned off, the stored electric charge in the capacitor can give a shock. They need to be fully discharged before replacement.

central air conditioner humming noise

Discharging an capacitor completely

- Take a screwdriver.
- Hold on to the insulated part of the screwdriver and make sure you don't touch the conductive metal.
- Put the metal of the screwdriver between the leads on the capacitor so that it bridges them.
- Hold the screwdriver for a minute and it will discharge the power stored in the capacitor.
- Use the circuit alert device to make sure that all the charge has leaked out of the capacitor.

What About Testing Using A Digital Multimeter

Testing the capacitor using a Digital Multimeter

- Discharge the capacitor completely using the method explained above.- Set 1000Ohm = 1k ohm range on the Multimeter.- Connect the capacitor to the meter terminals.- If it gives some reading and does not change after that, it means the capacitor is not working. - If it gives some reading and diverts to the open line, it means the capacitor is working fine.

Testing the capacitor using an Analog Multimeter

- Discharge the capacitor completely using the method explained above.- Select the meter on ohm and connect the capacitor to the meter terminals.- If the meter shows very low resistance and sticks there only, then it means the capacitor is dead.- If the meter first shows low resistance and then moves towards infinite, it means capacitor is working properly.

central air conditioner humming noise

Removing the capacitor

After discharging the capacitor, remove it from its place without disconnecting the wires. Take your cellphone and click the pictures of the capacitor so that the connections can be seen clearly later for reference. Make sure that the picture clicked can show you later which wire goes where and then disconnect the damaged capacitor.

Buying a new capacitor

The easiest way to get the correct replacement for your blown out capacitor is to just take the damaged piece and ask the retailer for a similar one. Make sure the microfarads rating on the new capacitor matches the damaged one. Capacitors don't cost much and are very easily replaceable. 


GE Genteq Replacement for Capacitor 30/5 uf 370 volt 97F9833, 370V, 30/5 MFD, Dual Run, Round Capacitorair condition

Return Me To Airfresha Home

Airfresha And More 2017 | All Rights Reserved.| Airfresha.com is a participant in the ClickBank and Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and Clickbank affiliated sites.