Microwave is tripping circuit breaker

If your microwave is tripping the circuit breaker, stop using it until you identify the cause. The most likely problem is a failed microwave door switch. Most models use three or four interlock switches, including the primary door switch, secondary door switch, and monitor switch, which must close in sequence. A defective switch can short the circuit, blow the line fuse, or trip the breaker when the door opens or closes. Less commonly, a shorted high-voltage capacitor, magnetron, or high-voltage transformer can cause a microwave to trip the breaker. A failed transformer may also arc or produce a burnt smell. Testing these parts with a multimeter can help confirm the problem, but opening the outer cabinet exposes a high-voltage capacitor that stores a lethal charge even after the microwave is unplugged. The capacitor must be properly discharged before any interior repair, and this work may require a qualified technician if you are not familiar with safe discharge procedures. Enter your model number to find the exact replacement door switch, capacitor, magnetron, or transformer for your specific microwave.

01 - Microwave Door Switch

Most microwaves have three or four door switches. When the microwave door closes, the door switches actuate in sequence to ensure that the door is closed properly. If any of the door switches fail, the microwave line fuse can blow, or the circuit breaker may trip. To determine if any of the door switches are defective, use a multimeter to test each of the switches for continuity. If any of the door switches lack continuity, replace the defective switch. (Caution: The microwave oven can store thousands of volts of electricity in its high voltage capacitor, even after the microwave oven has been unplugged. Due to the potenti...al for electric shock, it is extremely dangerous to replace the electronic components in a microwave. Only a licensed technician should replace a door switch.)

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02 - Microwave High Voltage Capacitor

A microwave that is tripping a circuit breaker can be caused by a shorted high voltage capacitor. You can determine that a capacitor has shorted by contacting one multimeter lead to one of the capacitor's terminals and the other lead to the casing. If meter display indicates that electrical continuity is present between any of the capacitor terminals and the casing, or the terminals show continuous continuity between them, the component has shorted and will need to be replaced.

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03 - Microwave Magnetron

A microwave that is tripping a circuit breaker can be caused by a shorted magnetron. You can determine that a magnetron has shorted by contacting one multimeter lead to one of the magnetron's terminals and the other lead to the casing. If meter display indicates that electrical continuity is present between any of the terminals and the casing, the magnetron has shorted and will need to be replaced.

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04 - Microwave High Voltage Transformer

A microwave that is tripping a circuit breaker can be caused by a shorted high voltage transformer. When a high voltage transformer shorts out, it will usually arc and smell burnt.

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Uncommon But Possible