Note: Before touching any internal parts, be sure to discharge the capacitor. The capacitor stores additional voltage and can hurt you even if the unit is unplugged. To discharge a capacitor safely, you will need the following: a screwdriver, a wire-wound resistor with a 2 watt-20,000ohm rating, and a pair of jumper wires with alligator clips on the ends. Clip a wire to each end of the resistor. Clip one wire to the metal shaft of the screwdriver. Clip the other wire to one of the capacitor’s terminals. Now, touch the other terminal with the tip of the screwdriver. There may be a small spark. If the capacitor has three terminals, do the same process with the middle terminal and each outside terminal.The microwave oven won’t run at all
Unplug the power cord and check for voltage at the outlet. Inspect the cord for any damage or burn marks. Because of all the safety devices in a microwave oven, any one of them could be the cause. You will need to remove the outside shell of the microwave. Unscrew the screws underneath and on the back that hold the shell in place and slide it off. Here’s a list of things to check that may be causing this problem.
The microwave oven won’t run at all
- The fuse could be blown — Remove the fuse with a set of fusepullers. Place it on a paper towel so it doesn’t roll away. With your VOM set to RX1, place a probe on each end of the fuse. The reading should be zero. If not, replace the fuse with an identical one.
- Door switch could be bad — Locate the door switches and remove the leads. With the VOM on RX1, probe the terminals. The reading should be infinity with the door open and zero with it closed. If not, replace. Check both door switches.
- Fan motor could be bad — Locate the fan and remove the leads. With the VOM set to RX1, probe the terminals. If the reading is infinity, then it is bad.
Check the voltage at the outlet supplying power. If it is lower than 115 volts, there is a problem with your electrical service or breaker. A bad turntable motor may also be the cause. To check it, turn the microwave over onto its top. Remove the bottom grill. Set the VOM to RX1 and remove one lead from the motor terminals. Probe the terminals. If the reading is infinity, then replace the motor. The magnetron and the wave guide may also be the culprits here. They need to be serviced by a professional.The microwave runs but it’s not cooking anything
Check the thermal cutoffs for both the oven and the magnetron. The thermal cutoffs are little disc shaped devices with a wire connecting the two of them. Remove a lead and set the VOM to RX1. Probe the terminals and look for a reading of zero. If not, replace. Check both thermal cutoffs. If these are OK, check the capacitor and diode as titleribed above. The magnetron or transformer could also be bad, but they need to be serviced by a professional.