I Recently had a VIRTUAL DIAGNOSTIC call with a client that had a “buzzing” sound coming from his air conditioner when it was turned on. I have come across this issue plenty of times in the past so I had an idea of what was causing this. I had the client turn off the power to the condenser by pulling the disconnect beside the unit and open up the electrical compartment. (24-volt power will still be activated to the contactor) This exposed all the electrical components to the condenser. It should be noted that even with the power off to the condenser, the unit continued to “buzz”. There is only one place that could still have power going to it, the contractor. (photo above)

The contactor takes 24-volts from the furnace control board and sends it to the contactor relay which closes its contacts and passes 240-volts from one side of the contactor to the other and activating the fan and compressor. Once we isolated the “buzzing” sound to the contactor, I had the client turn the thermostat off which killed power to the contactor. (If you have children or anyone else in the home, turn the power off to the furnace as well to avoid someone unexpectedly turning the thermostat on and then shorting out the control board). 

I then had the client go back outside and look at the contactor itself and see if there was any debris in the contacts and blow it out with some canned air. Sometimes debris such as spiderwebs and small insects can get in there and disrupt the contacts, causing a buzzing sound. Then I had them look closely at the contacts themselves to look for pitting. “Pitting” (shown in the photo above) is caused by oxidation and age and is similar to acne scars (you know the ones) left after acne clears up, except on these little, metal pads. In this case, that was exactly what was causing the issue.

This client was near one of our partner distributors, so I had the client order the new contactor that I sent him a link for and he picked it up. I emailed the client to be sure everything went smooth and he advised that he replaced the contactor and the unit was back up and running quietly in a matter of minutes! Another happy camper!

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