Sharp microwaves operate on the "ERR" error code display with a number following the error. The "ERR 3" code is one of the worst and may require a whole new microwave.
"ERR 3" means that the magnetron units have failed in the microwave. Food will not cook or heat up when the microwave is in use.
This code is different than "ERR 1" or "ERR 2" because with those the microwave is still operational. "ERR 3" means a complete failure.
The magnetron is the main source of power and heating in a microwave. Magnets work inside a magnetron tube to create the heat and voltage needed to cook items.
Bring the microwave back to the retailer or a repair shop for service. You may also consider purchasing a whole new microwave if the prices are cheap enough.
This error code mainly appears on commercial use Sharp microwaves but it is also found on several household microwaves.