Appliance Repair Questions? Ask a Technician for Answers ASAP
The fan control relay has stuck or fused in the on position.The relay is on the control board. You might persuade it to unstick by tapping its casing, but if its fused then you'll have to replace either the relay or the complete board.Or, you can just turn off the supply to the oven when it has cooled down.
I wrongly assumed, without asking, that the oven element switches off when the oven reaches the set temperature. If not, then the temperature control thermostat is faulty. It's also worth checking the high-limit thermostat as that can cause the fan to remain running.Replacing a relay would be a board-level repair, if you have the skills and tools to to do that. Otherwise it would be a new control board. If it comes to that I can find you the part number.
Well, I can't find a definition of "c3", but I believe the hob control board is a different part to the oven control board.When you wrote "there is no sign that the oven element didn't turn itself off", did you really mean "didn't" as that's a double negative?
OK. I understood the hob symptoms, but I would expect that to have its own control board - I think the hob and the oven are unconnected except that their share the power board.