Outside Air Conditioner Condenser Unit Not Turning Off

Why does an outside air conditioner condenser unit not turn off?

If your Outside Air Conditioner Condenser Unit Not Turning Off even after the inside blower motor stops you most likely have a defective or stuck contactor.

How to change a contactor if your Outside Air Conditioner Condenser Unit Not Turning Off.

The picture below is what a contactor on a home condenser air conditioner looks like.

Outside Air Conditioner Condenser Unit Not Turning Off
Picture of a new contactor.

The reason the ac condenser unit stays running even after the thermostat reaches the desired temperature is one of two reasons.

The number one reason is that the contacts that transfer power are stuck together. The contacts are typically made of silver or copper. Every time the thermostat reaches a temperature and sends voltage to the contactor it will engage. The contactor will engage many thousands of times per year.

Outside Air Conditioner Condenser Unit Not Turning Off
A picture of a contactor with burned sticking contacts

Even under normal usage the contactor contacts will eventually become damaged.

Diagnose AC Unit Not Coming On.

The contactor sticking or defective and stuck in the closed position is a common reason the AC condenser stays on when its supposed to shut off.

When this happens the evaporator coil inside and the copper refrigerant lines will form ice on them if the inside blower motor stays off too long.

Change Contactor

Before doing any repairs on the condenser make sure the power is turned off going to the condenser. In most cases the condenser will have an A/C disconnect by the outdoor condenser. You can simply shut the power off by pulling the fuses out or flipping a switch off. In some cases you will need to locate the breaker that is feeding power to the condenser.

Make sure the thermostat is in the off position.

It’s not mandatory but you may want to also have the power off to the inside furnace or air handler. This will totally ensure there is no voltage coming into the condenser while you are changing the contactor.

make sure to use a working and tested volt meter to ensure the power is off before touching the contactor or electrical components.

After the power is off use your phone to take a picture of all the wires on the contactor. You can also draw a diagram with the colors and the location of each wire and where they go on the contactor.

Remove each of the wires and then use a nut driver or screw driver to remove the screws holding the contactor on the frame of the condenser.

Screw the new contactor to the condenser frame. After the contactor is in place you will need to refer to the pictures and diagram to make sure you put the wire back in the same location. Make sure all of the wires are secure on the new contactor and and screws are tight.

Test The Condenser

Now that you have replaced the contactor you will need to turn on the power. Turn the power back on to the inside furnace or air handler. You will also need to apply the fuses back in the condenser disconnect and then turn the thermostat to the cool position.

Test the condenser by letting it run for a few minutes then go and turn the thermostat off to ensure the condenser shuts off.

Now that your condenser isn’t shutting off anymore you can sit back with your favorite beverage and relax.

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Frequently asked question

Question – Why is the Outside Air Conditioner Condenser Unit Not Turning Off? Answer – The reason a AC unit doesnt shut off is typically because the contactor is bad and sticking in the closed position.

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