The job of the outside fan on your HVAC unit is to blow air over the condenser coils to remove heat from inside your home. If the fan is not running, your home will become hot quickly. Below are some possible causes of this problem to better help you understand what is going on.
Problems with Contactor
The main component inside your outside HVAC unit is the condenser. The contactor is the part inside the unit that activates and deactivates the condenser via a switch. For example, when the temperature inside your home reaches above the temperature setting on the thermostat, the switch will turn on to tell the condenser that cool air is needed. The condenser then turns on, the fan will start running, and you will feel cool air blowing out of your registers. If the contactor on your HVAC system goes bad, the outside fan will not run.
Motor Burnt Out
The fan motor works constantly while your HVAC unit is running, and over time it will burn out due to too much stress. If the temperature of the inside of your home is higher than the temperature you have the thermostat set to, the fan on the HVAC unit is likely not running. This is a sign of a bad fan motor.
Belt Loose or Broken
If you have an older HVAC unit, the fan is powered via a belt. Over time, this belt will become loose or it may even break. When this happens, the fan will stop spinning. This problem can be repaired, but this may be good time to consider purchasing a new HVAC unit. Newer units are also more energy efficient so you will save money on your energy bills each month.
Problems with Capacitor
The capacitor is what provides power to the HVAC unit's fan. If something goes wrong with the capacitor, the fan would immediately stop working. Once the fan stops working, your unit may stop working completely or it will start to short cycle, which means it constantly turns on and off.
You should not attempt to fix any of these problems with your unit yourself, as you may cause even more harm. Instead, contact an HVAC contractor in your area to come to your home. They can diagnose the problem and then get the fan back up and running for you. Having your unit tuned up and maintained once per year can help prevent these problems from happening in the future.