The problem was a faulty lower fan ( this oven has an upper and a lower fan). Had to take front door off and had a little problem getting it off. On inside, had to remove nut that holds fan on, remove fan and sleeve over shaft(nut turned clockwise to loosen). I ordered new fan assembly complete with a conical shield and reinstalled sleeve. Important—shaft of new fan has different threads and must order new nut with new fan assembly. Old nut would not screw on. Sales agent alerted me to the need for new nut. Reassembled and now oven fan works fine. Be sure to place something under oven feet so doesn’t scratch floor