The answer to 'my air handler won't turn on' is that there are several common causes, including a tripped circuit breaker, faulty thermostat, or issues with the air handler itself. The air handler is the indoor unit of your HVAC system that circulates conditioned air throughout your home, and when it doesn't turn on, it can indicate a problem that requires troubleshooting.
Some of the most common symptoms of an air handler not turning on include no airflow from the vents, the system not responding to the thermostat, or unusual noises or smells coming from the unit. Potential solutions can include resetting the circuit breaker, checking the thermostat batteries and settings, or inspecting the air handler for any visible issues like loose wiring or debris buildup. However, if the problem persists or you're uncomfortable performing any repairs, it's best to call a professional HVAC technician to diagnose and fix the issue.