The answer to 'air filter not heating' is that a clogged or dirty air filter is a common cause of an HVAC system not heating properly. The air filter is responsible for trapping dust, debris, and other particles that can accumulate and restrict airflow. When the air filter becomes too dirty, it can prevent warm air from circulating effectively, leading to poor heating performance.
Other potential causes include issues with the thermostat, blower motor, or heating element. It's important to regularly replace or clean the air filter according to the manufacturer's recommendations, typically every 1-3 months. If the problem persists after changing the air filter, it's best to call a professional HVAC technician to diagnose and repair the issue.