What causes microwave ovens to fail?
The most common cause of microwave failure is its magnetron. The magnetron is what produces the microwaves that cook your food, and it's also the part that is most likely to burn out. Symptoms of a faulty or burned-out magnetron include a microwave that doesn't heat food properly or doesn't work.
How many years should a microwave last?
The average microwave oven lasts about seven years with normal use, and even less with heavy use and poor maintenance. A large family may find themselves replacing their appliance every four to five years as they become more reliant on its use to heat up snacks and leftovers, or to defrost meals.