There are 2 fans in this oven.1 is the main oven fan (1 in the back of the oven cavity) and one on the top that is a cooling fan which will only come on when it has been running for a while which is what you say happens when noise appears.the cooling fan will have no effect on the cooking performance but is most likely to start being noisy sometime in to the cooking cycle.You need to find which fan is noisy.reasonably easy to change but oven has to come out and be stripped down to gain access.Thermostat could also be an issue to cooking performance?.sounds like you have more than 1 issue going on here!
ck, January 2010
