AC unit wont turn on


Old 06-02-18, 11:47 AM
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Exclamation AC unit wont turn on

My AC unit wont turn on - I replaced the capacitor and it still wont start - When I turn on the ac unit it just makes this clicking noise near the capacitor - Stopped working last night after a bad thunderstorm - Video below - THANK YOU FOR ANY ASSISTANCE

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Last edited by PJmax; 06-02-18 at 12:01 PM. Reason: added pic
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Old 06-02-18, 12:06 PM
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Welcome to the forums.

The part I circled in the pic I posted is the contactor. That is what is buzzing. 24vac is applied to it from the thermostat. It needs 24vac to operate correctly on a call for cold.

If you look at the side you will see two small wires. One is yellow. I can't see the other side.
Turn power off/pull the disconnect to the condenser. Check those two wires for 24vac when the condenser should be running.

This 24v power comes from inside the house which is why the condenser can be unpowered.
Old 06-02-18, 12:14 PM
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The clicking you're hearing is likely the contactor (relay) closing/opening. The contactor is the rectangular device that's circled in the picture. The 240VAC comes in on the 2 terminals at one end, and when the thermostat calls for cooling, 24VAC is sent to the two side terminals, which energizes the coil and closes the relay, sending 240VAC to the other two terminals which feed the compressor and fan motor.

If you have a multimeter, here's what I would suggest you do. First, turn off the 240VAC to the outside unit. You should have an electrical disconnect near the unit. With the thermostat calling for cooling, take your multimeter and set it to AC volts. Measure the voltage between the two side terminals (small diameter wires going to them). You should measure ~24VAC. If you measure 0V, move your meter to where the control voltage (small diameter, 2 conductor cable coming from the house/air handler to the outside unit). There should be wire nuts where the wires coming from the house attach to the wires inside the outside unit. If you have 24VAC at the wire nuts, you may be low on refrigerant and the low pressure switch is opening. If you have 0V at the wire nuts, it's time to move inside the house.

Let us know what you find.

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