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Touchstone Heating & Air Inc. Blog

Air Conditioning Won’t Run? It May Be a Contactor Problem

electrical-componentsThe “no cool” is the most common air conditioning emergency call we get. Our technicians are available 24 hours a day, 365 days a year to rush out to help with whatever has caused and AC to stop doing its job.

There are several reasons for an air conditioner to stop working. A common one we’re going to look at today is a problem with a contactor. What’s a contactor? That’s as good a place to start as any …

The Contactor: The Start and Stop Lights for an AC

A contactor is an electrical component that controls when electricity flows to a motor, and functions something like a stoplight at an intersection (just without the cross traffic). When the contactor is open, no electricity is allowed to flow to the motor (red light). When the contractor is closed, electricity flows freely (green light).

An air conditioning has contactors for the motors that power the compressor and the fans. When the air conditioning system is running, the contactors are all closed to allow electrical flow to keep the motors running. The contactors open when the AC powers down. The thermostat sends the voltage charges that open and close the contactors. When you set the thermostat to cool your house, a voltage charge goes to contactors for the compressor and outdoor fan (and the indoor blower if it isn’t already running) to close them. When the thermostat registers it’s time to end the cooling cycle, it sends the voltage to open the contactors.

How Contactors Can Go Wrong

Like any electrical component, a contactor won’t last forever. Often the contactors in an AC will wear down years before the air conditioning system needs to be replaced. Enough wear on a contactor will cause it to burn out and stop working. A burnt-out contactor won’t allow its motor to run, and the air conditioner will not be able to provide cooling. (Losing the compressor or either fan is a “no cool” situation.)

Contactors can also become stuck in one position, and this can occur because of dirt getting into the system and along the contactor. A contactor that’s stuck in the open position or which can’t close completely because it’s blocked will stop motors from working. And when a contactor gets stuck in the closed position, it means electricity will flow continuously and the air conditioning system won’t turn off—or at least one of the fans or the compressor won’t shut off. This isn’t a “no cool” problem, but it’s still a serious one: you want a runaway AC fixed before it becomes even more seriously damaged.

Maintenance Helps Keep Contactors Working

An air conditioning service in Lake City, FL we strongly recommend is annual spring maintenance for the AC. Our technicians look over the contactors during these inspections to find out if they’re in danger of burning out so they can be replaced early. We also clean them if they’re dirty to help avoid problems with them becoming stuck open or closed. Regular maintenance gives you a good chance of never having to deal with a contactor problem.

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