Should the outside fan of an HVAC unit turn on when heat cycle is or does it only operate in AC cycle?

In most cases, the outside fan of an HVAC unit will turn on when the heat cycle is on. The fan helps to circulate the warm air produced by the furnace throughout the house. However, there are some cases where the fan may not turn on when the heat cycle is on. For example, if the outdoor temperature is very low, the fan may not turn on to prevent the warm air from escaping from the house. Additionally, some furnaces have a setting that allows you to control whether or not the fan turns on when the heat cycle is on. If you are not sure whether or not the fan of your HVAC unit should turn on when the heat cycle is on, you should consult with a qualified HVAC technician.