The pilot and gas burners start, but the fan does not. If the fan isn't working, that can cause the coil to freeze. Ac Fan Not Working Troubleshooting Air Conditioner Capacitor Repair - Youtube Air Conditioner Condenser Broken Air Conditioner Air Conditioning Unit If you or a tech has recently tampered with your furnace, it’s possible that the fan limit switch was set incorrectly by accident. Hvac fan not working heat . A bad odor from a central heating unit could mean a lot of things. When call for heat occurs, the furnace kicks in, and fan runs at full speed, as expected, however when operating with no call for heat, the fan is running very low. Set the thermostat to “heat” if you have a dual cycle system. The burner flame must be on and the heating chamber warm for these types of fans to work. Also, if the fan limit switch override (a small knob on the switch) somehow got set to manual instead of auto, the blower will run constantly—whether or not your furnace is go...