AEG double oven. High-pithced noise happens when we turn oven on. Changed the heating element as this was broken. The fan looks fine and working fine. It sounds as if it's coming from the Timer area. Any ideas?

There is a type of stethoscope that has a rod and is used in automotive applications. You can find one at: Amazon.com: Lisle 52500 Mechanic's Stethoscope: Automotive
I hope this helps.

Thanks but I'm not a mechanic or engineer, so this would be a waste of money. I need a solution, it starts as soon as I turn on the oven (just the light, not even the temperature) and doesn't stop until I turn it off. It starts even before I turn up the temperature and the only way to stop it after turning off the oven is to turn it off at the mains switch. Any ideas?