The answer to 'why is my HVAC system short cycling' is that your HVAC system is turning on and off rapidly, cycling through its heating or cooling process too quickly. This is a common issue that can be caused by several factors, including a system that is too large for your home, a clogged air filter, a refrigerant leak, or a malfunctioning thermostat.
Short cycling wastes energy, puts extra strain on your HVAC components, and can lead to more serious problems if not addressed. It's important to identify and resolve the underlying cause to restore your system to proper, efficient operation.