Sparking in a Frigidaire microwave oven is most commonly caused by a damaged waveguide cover or rack support. To troubleshoot, owners can remove the suspected parts and verify whether the sparking still occurs when operating the microwave.
A waveguide cover should be replaced if it is burnt or does not stay in place. Any damage to the inside top or walls should be repaired and painted with microwave paint. The manufacturer number for a replacement waveguide for a Frigidaire microwave is 5304475705.
Rack supports that cause sparking should be replaced, and any bare metal should be painted using microwave paint. The manufacturer numbers for replacement left and right rear rack supports are 5304473093 and 5304473094, respectively.