how can We sort the rattling noise from the fan when turning on the lower oven

Margaret, December 2016

More likely to be the element around the fan has buckled and bent and is now touching the fan blade. Take the cover off & look. If element is bent then replace the element. Don't go bending the fan blades as a temporary fix. Do the job once & do it properly.

Lincoln Appliance NZ, December 2016

Fan blades in cookers are usually made from aluminium - with the passage of time the constant heating and cooling can cause one of the blades to bend - what you hear is very probably a bent blade going clang clang against a near object.

If the fan is on the back wall of the oven then remove the cover plate and adjust the bent blade.

Or - if you're short of confidence - call in an engineer or a friend.

Good Luck..., December 2016