Bush oven shows E04 and the cooling fan or oven fan does not run, or the oven shuts down shortly after starting.

Safety first: Isolate the oven from the mains. Fans can start unexpectedly and sharp metal edges are present.

• Determine which fan is affected: On many Bush ovens, E04 relates to the cooling fan that runs above or behind the cavity. Listen for any attempt to start or humming before the error appears.
• Access the fan: Remove the oven from the housing. Take off the top or rear panel to expose the cooling fan assembly or rear convection fan.
• Check for obstruction: Ensure no insulation, wiring, or debris is fouling the fan blades. Manually spin the fan; it should rotate freely. If stiff or seized, the motor likely needs replacement.
• Test the fan motor: Disconnect the fan connectors. Measure resistance across the motor terminals. An open circuit indicates a failed motor. Compare to a known-good value if available.
• Inspect wiring and connectors: Look for heat-damaged wires near the fan. Repair or replace as needed using high-temperature cable.
• Control board output: If the fan motor tests good, the fan drive relay or triac on the PCB may be faulty. This typically requires PCB replacement or specialist repair.