Your HVAC system has a fan in it that is an essential component that helps the unit run. If your fan fails, the HVAC system can't move the air it produces through your entire home. A fan can stop working for several reasons, and here are two of them that are common.
One reason that the fan stopped working suddenly might be that you have a bad capacitor. Think of a capacitor like a battery. They have energy inside them, and they use it to start your HVAC system's fan and keep the part running. When the capacitor is not working properly, it could cause problems with the fan being unable to stay on or having difficulty turning on at all.
The capacitor can stop working for a few reasons. It's possible that the capacitor has simply worn out from years of use, and it can no longer hold any charge. It's also possible that a power surge damaged the capacitor. You may hear clicking sounds coming from the capacitor in either of these situations, which is a sign that it has gone bad.
To test the capacitor, use a small stick to push on the blades of your fan. If your fan doesn't start spinning afterward, then you have a capacitor problem. If your condenser outside is running and the fan is not spinning, it's most likely a capacitor problem as well.
The contactor is the part that helps regulate how much electricity goes to the compressor and fan. If the contactor is failing, it can stick and not turn off or on any of the motors. It not only results in a malfunctioning fan, but could damage the compressor by causing it to run too long. This runs the risk of burning out the compressor, which could require the entire unit to be replaced. That's why you'll want to repair a contactor problem as fast as you can.
You can use a couple techniques to diagnose a contactor problem on your own. Start by turning on your air conditioning and listening. If you do not hear the compressor or the fan running, it could be due to a faulty contactor. A multi-meter can also be used to test your contactor, since it will show power going into the unit but no power going out of it.
For help repairing either of these problems, work with a local HVAC contractor at a company like Scott's Heating & Air Conditioning Services.