Safety first: Isolate power and gas. Wait for moving parts to stop before touching the fan assembly.

Visual inspection: Remove the combustion chamber cover and inspect the fan wheel for dirt buildup, foreign objects, or signs of rubbing against the housing. Clean carefully if accessible.
Check wiring: Verify that the multi-pin connector from the fan to the main PCB is fully seated and free from corrosion or heat damage.
Spin test: Gently rotate the fan wheel by hand. It should turn smoothly without grinding or excessive play. Stiffness or noise indicates bearing failure and the fan should be replaced.
Electrical tests (qualified): A technician can measure fan supply voltage and tachometer signal at the PCB during operation. If the fan is powered but not running, or no speed feedback is detected, replace the fan assembly.
PCB diagnosis: If a known-good fan still triggers F7, the control board’s fan control circuit may be faulty and require replacement.

Furnace displays F7, fan may run continuously, burner does not ignite

Possible Causes