I have started running my furnace for the season. As the furnace is running I hear the following noises coming from the condenser, usually at night.
The unit is running and I will hear a buzzing noise coming from the condenser unit. The fan on the condenser is still running while I am getting the buzzing. Sometimes the buzzing seems to pulsate. After a few minutes of buzzing the unit will shut off and the buzz will give way to a brief "swoosh" type of sound.