The main steps in microwave troubleshooting are identifying the problem and inspecting the different parts that are likely to be the source of the problem. Common issues include failure of the unit to power on, sparks during operation and turning off after a few seconds.
If the unit does not work at all, the microwave fuse may be blown and require replacement. The fuse exists to protect the microwave from electrical currents that are too strong and cuts off the power flow if necessary. In the event of a blown fuse, the microwave can only operate again after a new fuse is installed. A defective door switch may also explain why the microwave is not working.
Sparks may result from splattered or dripped food or grease on the inside of the microwave. Cleaning out the unit thoroughly may be all it takes to stop the sparking. If this does not resolve the issue, a more technical problem, such as a stirrer that is not working, might be causing the sparks. The stirrer may fail to work if either the stirrer belt or the fan motor is broken.
Issues with several different parts of the microwave can cause it to turn off after a few seconds. The door switch, main control board, touchpad, thermostat and thermoprotector should all be inspected for damage. A malfunctioning high-voltage transformer may also be the root of the problem.