The answer to 'air handler not heating' is that there are several common causes, including a malfunctioning thermostat, issues with the heating element or compressor, or problems with the air handler itself. Symptoms may include the air handler running but not producing warm air, or the system not turning on at all.
Some potential solutions include checking the thermostat settings, inspecting the air filter and replacing it if needed, and verifying that the power supply to the air handler is working properly. If the issue persists, it's best to call in a professional HVAC technician to diagnose and repair the problem, as they have the expertise and tools to properly identify and fix the root cause.