How To Fix A Microwave That Isn't Heating
- Rated as REALLY EASY
- 21 repair stories
- 3 step by step videos
High Voltage Diode
If your microwave oven doesn’t heat, you may have a problem with the high voltage diode or rectifier. This component helps provide the high voltage that powers the magnetron. The high voltage diode is located near the magnetron and the high voltage capacitor, so access will require removal of the cabinet. Disconnect the power and also discharge the high voltage capacitor to prevent an electrical shock. You can then test the diode for continuity with a multi-meter. Diodes are polarity specific and you should see low resistance with the meter leads in one direction and higher resistance when the meter leads are reversed. Most multi-meters will have a special setting for diodes or rectifiers. If the high voltage diode shows low resistance in both directions or shows no continuity at all, then it will need to be replaced. If you find the high voltage diode tests okay, then you will need to determine whether power is being supplied to the circuit. This is a high voltage circuit and further testing should only be performed by a qualified technician.
Door Switch
If your microwave oven doesn’t heat, you may have a problem with a door switch. The door switches, often referred to as interlock switches, provide power to the various components in the microwave when the door is in a closed position, and interrupt power when the door is open. Sometimes it is possible that when an interlock switch fails, the fan motor and or stirrer motor may continue to operate but the magnetron won’t. The interlock switches are located inside the cabinet and are activated by hooks or latches on the door. Unplug the unit and remove the cabinet. The interlock switches will have wires attached to the terminals marked common (C) and normally open (NO). Check the switches for continuity using a multi-meter. With the actuator button depressed, you should see continuity between these terminals. If there is no continuity the switch will need to be replaced. You should also verify that the door hooks properly engage the switch actuator when the door is closed and adjust if necessary.
Magnetron
If your microwave oven doesn’t heat, you may have a problem with the magnetron. This component is part of the high voltage circuit and provides the microwaves that generate the heat. If the magnetron is defective, the unit may blow a fuse, or you may still have all other functions operating normally. Access to the magnetron will require removal of the cabinet. Disconnect the power and discharge the high voltage capacitor to prevent an electrical shock. You can then locate the magnetron and disconnect the two attached wires. Attach the leads from a multi-meter to the magnetron terminals and check for continuity. There should be only 2-3 ohms of resistance between these terminals. If there is no continuity, then the magnetron will need to be replaced. Also, check for continuity between both terminals and the grounded outer case of the magnetron. If there is any continuity between either of the terminals and ground, the magnetron will need to be replaced. If the continuity checks do not reveal any defects, then live voltage tests may be required and should be referred to a qualified person.
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