The answer to 'why is my evaporator coil short cycling' is that the evaporator coil is rapidly turning on and off, causing your HVAC system to cycle frequently. This can be caused by a variety of issues, including a dirty air filter, low refrigerant levels, or a malfunctioning thermostat. Short cycling can lead to increased energy bills, uneven cooling, and potential damage to your HVAC system.
If you're experiencing short cycling, it's best to have a professional HVAC technician inspect your system. They can diagnose the underlying issue and provide the appropriate solution, whether it's cleaning the air filter, recharging the refrigerant, or replacing a faulty component. While some minor troubleshooting may be possible as a DIY task, HVAC systems are complex and require specialized knowledge to repair properly.