The compressor is located in your outdoor unit. It's responsible for pumping refrigerant from that outdoor unit to the one located inside your house. The compressor is partially responsible for removing heat from the air, so it needs to disperse that heat. That's where the compressor fan comes in — it ventilates the inside of the unit.
If your compressor fan stops working, the compressor itself can no longer function properly. Indeed, it may overheat and burn out. You'd want to have the fan repaired before the compressor stops working. Below are some reasons it might stop functioning.
Electric Control Fails
Electricity naturally controls the movement of your compressor fan. The electricity has to run through a control, which triggers both the compressor and its fan to work. A mid-sized AC unit can lead to cycling, which is when your air conditioner turns on and off without much pause between. That cycling can lead to wear on the electric control, and it will fail.
Capacitor Goes Bad
The electricity goes through a capacitor to jolt the fan into moving. The capacitor stores the energy. Your compressor unit will contain a start capacitor that must store a lot of energy to get the relatively heavy fan turning. As with the electric control, a capacitor can wear out, especially if it's overused. In that case, it won't be able to jolt the compressor fan into turning.
Motor Burns Out
Naturally, the fan itself is attached to a motor, which is the method of turning. As with any motor, it needs a good cleaning and lubrication periodically. If it doesn't receive attention, it can develop a grimy buildup. This buildup especially happens if the air filter is dirty. The motor can seize up if it's not properly lubricated, which can cause the entire motor to burn out.
Fan Belt Breaks
On modern systems, the compressor fan attaches to a rod that's also attached directly to the motor, which is how it turns. In older units, a belt goes around the compressor motor and attaches to the fan to revolve it. The fan wears out over time and either becomes loose or breaks. When that happens, it no longer revolves the base of the fan.
Another issue that can strike the compressor motor has to do with the circuitry. Sometimes different parts of the air conditioner overheat, which then trips your circuit breaker. However, the overheating can also overload your AC circuits. If your air conditioner keeps tripping the circuit breaker, it probably has a circuitry issue that needs repair.
If you think your compressor fan isn't working, call for air conditioner repair.