Safety first: Disconnect mains power. Cooling fans are near live parts; avoid contact with wiring.

Steps:

Observe behaviour: If the fan never runs, overheating may also occur. If it runs constantly even when cold, suspect a stuck relay or thermostat.
Access cooling fan: Remove the top cover of the oven housing to access the tangential cooling fan assembly.
Check for obstructions: Ensure no insulation or wiring is fouling the fan blades.
Test motor: Disconnect the fan and measure resistance across the motor terminals. An open circuit indicates a failed motor. If possible, briefly power the motor with a suitable test lead (only if you are qualified) to confirm operation.
Check thermostat/relay: Locate the cooling fan thermostat (often clipped to the top of the cavity). Test continuity at room temperature and when gently warmed with a hair dryer. If it does not switch as specified, replace it. If the thermostat is OK, the control board relay may be stuck and the electronic control board may need replacement.

Warning: Do not operate the oven without a functioning cooling fan; this can cause serious damage.

Morphy Richards oven displays E8 and the cooling fan runs continuously or not at all.

Possible Causes