The part(s) or condition(s) listed below for the symptom Microwave is loud or noisy are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.
The magnetron uses high voltage, high current DC power to generate the microwave frequency that cooks the food. Under normal circumstances, the magnetron emits a low hum. However, if the magnetron is damaged or nearly burned out, it may begin emitting high-pitched sounds or growling noises. If the magnetron is noisy, this indicates that the magnetron is nearing the end of its life or might be defective. A defective high-voltage diode can also cause the magnetron to be loud. Before replacing the magnetron, first test the high voltage diode. If the diode is not defective, replace the magnetron. (Warning: The microwave oven can store a lethal amount of electricity in its high voltage capacitor, even after the microwave oven has been unplugged. Due to the high running voltage and the potential for electric shock, it is extremely dangerous to replace the electronic components in a microwave. Only a licensed technician should replace the magnetron.)
To determine if the fan motor is defective, remove the fan motor from the microwave and try turning the fan blades by hand. If the blades do not turn freely, replace the fan motor. If the fan blades do turn freely, use a multimeter to test the motor for incoming power and for continuity. If the motor has power but won’t run, replace it. If the motor does not have continuity, replace it.
The stirrer is a metal blade which slowly rotates inside in the microwave. As the stirrer turns, it deflects the microwave energy randomly throughout the microwave. As the stirrer motor wears down, it begins to make grinding noises. To determine if the stirrer motor is worn out, check to see if voltage is getting to the motor. If the motor has the proper voltage, but is noisy or won’t turn, replace it. (Note: Proper voltage can be determined by reading the label on the motor. Because the stirrer motor is a geared motor, the shaft will not spin freely.)
To determine if the turntable motor is worn out, check to see if voltage is getting to the motor. If the motor has the proper voltage, but is noisy or won’t turn, replace it.