Microwave displays F8 and may shut down or refuse to start, often related to cooling or fan operation.

Safety: Turn off power at the breaker and unplug the unit before servicing. Blades and sheet metal edges can be sharp.

• Check vents: Inspect all front, top, and rear vents on the Viking microwave for dust, grease, or obstructions. Clean thoroughly and ensure proper clearance around the unit.
• Listen for fan: When the unit is started (if it will run), listen for the internal cooling fan. If it is silent or noisy, the fan may be failing.
• Access fan motor: Remove the outer cabinet to locate the cavity cooling fan (usually near the top or rear). Check that the fan spins freely by hand and that no debris is blocking it.
• Inspect wiring: Verify that the fan motor harness is securely connected to the motor and the control board.
• Replace fan motor: If the fan is seized, noisy, or not receiving power when commanded, replace the Viking cooling fan motor assembly.
• Control board check: If the fan motor tests good but never receives power, the fan relay or control board may be defective and require replacement.