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Problem: My Carrier AC unit is cutting off and on. What could cause this?

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Problem: I have a Carrier central AC unit. It stopped working yesterday.
The symptom is: once I turn the AC on, you will hear the clicking sound from inside condensing unit outside door. I took off the control cover and saw the contactor (relay) pole is closing, then open. If I pushed down the pole (metal bar) into close position, the AC will start running, but the non-stopping click sound from inside the unit is still there (about 1 – 2 seconds interval). Once I not push it, AC stopped and the clicks sounds (two: one from contactor and the other from inside unit) resume. Note: I saw the burn out sign of contactor and replaced the contactor but the issue remain. Is there a relay or device that can make the click sound inside unit? Is that something I can replace by myself? Any suggestion for trouble-shooting? Thanks in advance, Rick

Answer: Thanks so much for your interest in our website and the opportunity to do business with you! This sounds like you might be low on refrigerant charge and the low pressure switch on your unit (if equipped many Carrier units are equipped with low pressure switches) is kicking the contactor off for protection. This is a safety device that will not allow the unit to run if the unit is low on refrigerant charge. I would suggest that you have your refrigerant charge checked to make sure your system is charged up properly. Another cause for contactor chatter or for a contactor not closing all the way could be a weak low voltage transformer or a thermostat that needs the battery changed. Contactor chatter and kicking off and on will cause a contactor to burn out quickly. I have seen these problems when I was doing HVAC service work. Please click here if you are interested in good universal low voltage transformer. Please click here if you are interested in a new contactor. Please email us anytime if you have questions. Our email address is: We would love to help you out and have your business! Best of luck in finding the problem. I hope that you have a great day!

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