How To Fix A Microwave That Won't Stop Running

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  • Rated as REALLY EASY
  • 4 repair stories
  • 2 step by step videos

Door Interlock Switch

If your microwave oven doesn’t appear to shut off when the door is open, you may have a problem with the door switch. The door switches, often referred to as interlock switches, provide power to the various components of the microwave. They are designed to interrupt the power when the door is open. In certain situations when an interlock switch fails, the interior light, fan motor, or stirrer motor may continue to operate after the microwave oven door is opened. The magnetron will not operate because of a failsafe monitor switch. 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). You can check the switches for continuity using a multi-meter. The closed door will depress the actuator button on the switch; you should see continuity between these terminals. When the door is open there should be no continuity, and if there is the switch needs to be replaced.

Smart Board

If your microwave oven doesn’t shut off until the door is opened, you may have a problem with the control board. The control board, sometimes referred to as the Smart Board, powers the relays that control the various functions of the microwave. If the control is defective it may not shut off a relay when the function is complete, and then opening the door to interrupt the power to the control would be the only way to terminate the cycle. If you have this symptom, the control board may be at fault. Unplug the unit and remove the cabinet. If the relays are not part of the control board, you should check the output terminals on them for continuity first. There shouldn’t be continuity when the relay is not powered. If the relays check okay, then the control board is likely defective.

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