The 2 most common part(s) or condition(s) which cause the symptom Oven fan keeps running are listed below starting with the most likely. Check or test each item and watch any available videos.
RepairClinic Item # 1086191
The oven control board has a set of relays that turn on and off power to the bake, broil and fan circuits according to the customer settings and sensor input. If the oven fan keeps running, one of the relays might have shorted out. You can check the wiring diagram and with a meter check for voltage out from the control board. If voltage is always present from the fan relay, it is shorted and the control board will need to be replaced.
RepairClinic Item # 251863
When the oven fan keeps running after the oven has been switched off and cooled down the oven thermostat is often to blame. As the oven heats up the thermostat sends electrical current to the oven fan to keep the internal components cool. Once the appliance cools down the oven thermostat should turn the fan off. If the oven fan keeps running the oven thermostat will have to be replaced.