I have just had exactly the same problem.... bought a new ceramic classic rangemaster two weeeks and found that there is a cooling fan on the back that sounds like a jet engine every time the oven or grill are turned on. Have had the engineer out to change the fan, but there is no difference.....have complained to customer services and sent a recording of the noise to Rangemaster ...but they couldn't care less, won't allow me to speak to an engineer and keep saying that noone else has complained and this noise is normal ! It's terrible....sounds as if there is a loud vaccuum cleaner on in the kitchen and totally ruins the atmosphere in the adjacent dining room. I am so miserable and disappointed. This seems to be a serious design fault and it's outrageous given the cost of the cooker. I am wondering whether to post the video files on facebook to see if anyone else has had this probem.
I would be very sad to send the cooker back as it looks good ....but the noise is just unacceptable.Has anyone found a way to deal with this problem?