Microwave Not Heating Food? Diagnose Before Replacing It
Your microwave runs and the light turns on but food stays cold. Here is what is wrong and whether it is worth repairing.
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Why Microwaves Stop Heating
If the turntable spins and the light is on but food stays cold, the magnetron (the component that generates microwaves) has likely failed. Other possible causes include a failed high-voltage diode, a burned-out capacitor, or a faulty door switch that tells the microwave the door is not fully closed. A simple test: place a cup of water in the microwave and run it for one minute. If the water is not hot, the heating system has failed.
The Door Switch Test
Microwaves have 2 to 3 door switches that must all engage for the microwave to operate at full power. If one switch fails, the microwave may run but not heat. Listen for a clear clicking sound when you close the door. If the door feels loose or does not latch firmly, a switch may be broken. Door switches cost 5 to 15 dollars each and are relatively easy to replace, but accessing them requires removing the outer casing which involves safety precautions.
Important Safety Warning
Microwaves contain a high-voltage capacitor that stores lethal amounts of electricity even when the microwave is unplugged. Do NOT open the microwave casing unless you have experience with high-voltage electronics and know how to safely discharge the capacitor. The capacitor can hold thousands of volts for hours or days after unplugging. Unlike most home appliances, microwave internal repair can be genuinely dangerous for untrained individuals.
Repair vs Replace
If the magnetron has failed, repair parts cost 50 to 100 dollars plus labor. A new countertop microwave costs 60 to 150 dollars. For microwaves under 3 years old or high-end built-in models, repair makes sense. For standard countertop microwaves over 5 years old, replacement is almost always cheaper and easier. Over-the-range microwaves cost more to replace (200 to 500 dollars plus installation), so repair may be worthwhile up to about 8 to 10 years of age.
