Door Switch
If the microwave runs for a few seconds and then shuts off, a door switch might have failed intermittently. Check each of the door switches for any signs of overheating, arcing, or burning. Also check each of them for continuity. Replace any of the switches that is visibly damaged or that only has continuity intermittently.
Main Control Board
If the microwave runs for a few seconds and stops there may be a short circuit in the main control board. Check other components first, these boards are often misdiagnosed.
Touchpad and Control Panel
If the microwave runs for a few seconds and stops the touchpad and control panel might be defective. There are several other components that can cause this problem, be sure to check any other components before replacing this board.
Touchpad
If the microwave runs for a few seconds and stops the touchpad might be at fault. This is not common. Generally speaking, if the microwave display is working and some of the buttons respond correctly but some don’t, the problem is with the touchpad.
High Voltage Transformer
If the microwave runs for a few seconds and stops the high voltage transformer might have an intermittent short. This is not common. Check other components related to the microwave symptom first.
Thermoprotector
If the microwave runs for a few seconds and stops the thermoprotector may have tripped. This is a safety device to prevent the microwave from overheating. It can be tested for continuity to see if it's blown.
Thermostat
If the microwave runs for a few seconds and stops the thermostat might be defective.
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