The 1 most common part(s) or condition(s) which cause the symptom Microwave is sparking or arcing are listed below starting with the most likely. Check or test each item and watch any available videos.
RepairClinic Item # 1194879
If the microwave is sparking or arcing the waveguide cover might be damaged and shorting out. Try removing the waveguide cover and see if the problem goes away. If there are any damaged spots in the microwave ceiling or sidewalls, repair them and paint them with microwave oven paint. Replace the waveguide cover if it is burnt or if it will not stay in place.