The part(s) or condition(s) listed below for the symptom Microwave shuts off after a few seconds 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.
A door switch might be failing intermittently. Check each of the door switches for signs of overheating, arcing, or burning. If you don’t see any obvious signs of failure, use a multimeter to test each switch for continuity. If any of the switches is visibly damaged or only has intermittent continuity, replace it.
Control boards are often misdiagnosed—before replacing the control board, first check more commonly defective parts, particularly the door switches. If all of the other components are working properly, replace the control board.
To determine if the touchpad and control panel are defective, try pressing each of the buttons on the control panel. If some of the buttons respond correctly while others don’t, replace the touchpad and control panel.
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.
Microwave ovens produce a very high voltage in order to power the magnetron antenna, which emits the energy that cooks the food. When a high voltage transformer fails, it will usually arc and have a burning smell. (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 high voltage transformer.)
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.
If the microwave runs for a few seconds and stops the thermostat might be defective. Watch our video on testing thermostats.