Is a humming air conditioner affecting the peace and quiet around your home?

Manufacturers strive to reduce the noise level produced by the outdoor half of central A/C systems. Properly maintained and fully functional, the unit should make a polite whooshing sound that’s not a great disturbance to you (or your neighbors). A conspicuously loud humming air conditioner, on the other hand, generally indicates that something’s gone wrong somewhere. Here are some likely possibilities:

Weak Start/Run Capacitor

The powerful compressor motor located in the outdoor unit of a central air conditioning system requires a substantial jolt of electricity to actuate. A large start/run capacitor provides that initial voltage surge. Over the years, however, the capacitor weakens and no longer delivers sufficient electrical punch to do the job. This causes the compressor motor to emit an audible “humming” sound as it strains to start every time the thermostat signals the unit to cycle on. A failing start/run capacitor is a replaceable component at reasonable cost. Due to the danger of high voltage, replacing the capacitor should be handled by a qualified HVAC service technician only.

Defective Contactor Switch

Like the start/run capacitor, the contactor switch located in the outside unit performs a vital electrical function. When the thermostat wants more cooling, it sends a low-voltage signal to the contactor. This spring-loaded solenoid then switches the heavy-duty critical components including the compressor and condenser fan over to higher 240 volts needed for operation. A worn, defective contactor may make a chattering sound or a loud humming noise. Professional diagnosis is required to pinpoint the problem and safely replace this critical component.

Seized Fan Motor

The condenser fan in the outdoor unit blows air through the condenser coil to disperse heat extracted from inside your house. A worn-out fan motor may eventually lock up entirely and refuse to rotate, instead emitting only a loud hum. Often, it will trip a circuit breaker, too. Replacement requires dismantling the unit and is a job for a qualified HVAC technician only.

For all your home or business HVAC needs, contact the experts at Jackson & Sons.

Jackson & Sons, Inc.

Our goal is to help educate our customers in Eastern North Carolina (including Wayne, Johnston, Greene, Lenoir, Pitt and Duplin Counties) about energy and home comfort issues (specific to HVAC systems).