Re: Buzzing coming from AC unit after it shuts off
The buzzing you are hearing is probably the contactor or more likely a transformer. The contactor is not usually going to be energized unless there is a call for cooling; then it draws in the contacts (via 24 volts) and allows the power circuit (usually 208/230v) to be completed. It is more likely that the transformer (24v) is humming and since it is mounted on the cabinet, comes across like 'buzzing,'
If you have a heat pump then the sound could be from the reversing valve depending on whether it is energized in the heating mode or the cooling mode. This would only be if you had a heat pump though and not regular central air conditioning.
If you are concerned (which obviously you are otherwise you would not be asking) have a professional come out and go through the system. Not a bad idea anyway. Much better to address a 'little buzz' before it becomes a 'big boom.'
All the best, Irishmist
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