Problem: I pulled the high voltage disconnect on my outdoor unit. Why am I still getting a low humming sound?
Answer: The low humming sound is probably coming from your low voltage transformer. The power to the low voltage transformer is constantly on. The hum could also be the contactor or reversing valve coil on a heat pump being energized. The low voltage power transformer is usually located on the indoor furnace or air handler, but I have seen low voltage transformers housed inside outdoor air conditioner or heat pump units. Below we have a picture of a universal low voltage transformer that we sell. Please click here if you would like to see the low voltage transformer that we sell. I would suggest turning the power off to the furnace or air handler. This should kill the low voltage power that is going to your outdoor unit. Usually there is a switch on the side of the furnace to do this. On an air handler there are usually breakers or a disconnect. The low voltage will not hurt you, but if you accidentally touch a low voltage wire and ground it out then you might damage your board or blow a low voltage fuse on the board. Best of luck on finding your problem. If you have any other questions please email us anytime. Our email address is: firstname.lastname@example.org or comment below. We would love to help you out and have your business!