everything works but nothing will heat up.
You will want to check the magnetron and the magnetron thermostat. When checking the magnetron, looked for a cracked magnet and do a resistance check which should read less than .5 ohms. The thermostat you would check continuity. No continuity means that it is faulty and needs replaced.
Microwave actually turns on and runs when the door is opened. Lots of helpful answers here suggest replacing three door switches. My question: If I'm willing to buy all three and replace them all, can I do that as an amateur, or does it requires soldering and test equipment?
Answer Hello Tom,
You can certainly do this as an amateur. If you have a Phillips head screwdriver and about 30 minutes, you can do this. Start by unplugging the unit or turning off the breaker. If it is a breaker, verify that the power is off to the unit before proceeding. Remove the two screws along the top edge of the unit and remove the air grille. Now remove the screw centered above the control area. Now lifting and pulling out the control panel will remove it. Be aware that there are wires to this control and if they are removed, you should first take several pictures from different angles to aid in the re-wiring process. Now the door latch assembly containing the door switches is on your left. There should be two screws retaining it. It can now be removed, being careful of the wires. I normally remove the first switch from its' mount and transfer the wires, one at a time to avoid confusion. once the three switches have been replaced and wired, re-assemble in the reverse order of these instructions.