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Microwave oven · Repair Copilot

Microwave not heating

A microwave that runs but won't heat — turntable turning, light on, timer counting, but food cold — usually has a failed magnetron, high-voltage diode, or capacitor. On a microwave this no-heat fault is one you diagnose from the outside only: the internal high-voltage capacitor can hold a LETHAL charge even after unplugging. Show SightLine the microwave and SightLine walks you through the safe outside checks — and why the inside is off-limits.

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Steps to fix microwave not heating

  1. SAFETY — DO NOT OPEN THE MICROWAVE CABINET: the high-voltage capacitor inside can hold a lethal electric charge for a long time even after it's unplugged. This is not a DIY internal repair.
  2. First rule out the simple stuff you can check from outside: try a full minute on HIGH with a cup of water to confirm it truly isn't heating.
  3. Confirm the door closes and latches fully — a microwave won't heat if the door interlock thinks it's open.
  4. Unplug it for a minute and plug it back in to clear a control glitch, and make sure it's on a live outlet, not a tripped GFCI.
  5. Check you didn't leave it in a low power level or a defrost/timer-only mode that doesn't run the magnetron.
  6. If it still runs cold, the magnetron, diode, or capacitor has failed — because of the lethal capacitor charge, this is a job for a qualified appliance technician, and for a cheap countertop unit, replacement is usually smarter than repair.

Safety first: if a step calls for gas, a main water or sewer line, a service panel or main breaker, or a sealed refrigerant system, stop and call a licensed pro — Repair Copilot will tell you when you're there.