The answer to 'why is my air handler not heating' is that there are several common causes, including a malfunctioning thermostat, issues with the heating elements or heat pump, or problems with the air handler itself. Some key symptoms to look for include the air handler not turning on, the air not getting warm, or the system blowing cold air.
Some potential solutions include checking the thermostat settings, inspecting the heating elements or heat pump for any issues, and ensuring the air handler is receiving power and operating properly. However, it's important to note that HVAC systems can be complex, and it's generally recommended to call a professional technician to diagnose and repair any issues, especially if you're not comfortable working on the equipment yourself.