Microwave runs but doesn't heat

What this symptom might mean

When the light comes on, the turntable turns and the fan runs, but the food stays cold, the control side is working and the high-voltage side is not. Before assuming a failure, rule out the settings: a timer running instead of a cook cycle (GE lists this first), a power level set to 10 percent, a delay start, or a demo mode that runs everything except the heat. A door that has not latched fully will also stop the heat while the light stays on, and a worn door switch can do the same.

Beyond that, the possibilities are inside the sealed cabinet: the magnetron, the high-voltage diode, the capacitor, the high-voltage transformer, or a door interlock switch. GE's support page says plainly that it offers no do-it-yourself advice for microwaves because the capacitor can retain a dangerous charge after unplugging. We say the same. Whether that repair is worth doing depends almost entirely on what kind of microwave it is, which is covered below.

Safe checks you can do first

1. Settings. Cancel everything, then set a fresh cook cycle at full power for one minute with a cup of water inside. Check that Timer, Delay Start, Demo or a low power level was not selected. Look for a lock or L code on the display.
2. Door. Open the door and close it firmly until it clicks. If the door does not close squarely or feels loose, stop; a door that cannot latch is a reason to book, not to keep trying.
3. Reset. Unplug the microwave (or switch the breaker off for a built-in) for one minute and try again. Nothing more than that.
4. Power. If it is a countertop unit, plug a lamp into the outlet. Do not run a microwave on an extension cord or a shared power bar.
5. Water test. Heat 250 mL of water for one minute on full power. If it comes out hot, the microwave is heating and the earlier problem may have been settings or a food-load issue. If it is cold, the high-voltage side is not working.

Nothing above involves gas, wiring, refrigerant or removing panels. Those are technician-only: Removing the cabinet cover for any reason; Discharging or testing the capacitor, diode, transformer or magnetron; Adjusting or replacing the door, hinges, interlocks or waveguide cover if it involves opening the cabinet.

Repairs a technician may recommend

After inspection, not from the symptom alone.

• Door switch or interlock replacement. When the door does not register as closed. A modest repair that is usually worth it on any built-in or over-the-range unit.
• Magnetron replacement. When the magnetron has failed. Often worth it on a built-in, drawer or over-the-range unit; rarely worth it on a basic countertop model.
• High-voltage diode, capacitor or transformer replacement. When one of those has failed; the technician discharges the capacitor before any test.
• Control board or relay replacement. When the control never energises the high-voltage circuit.
• Replacement recommendation. On a countertop microwave of ordinary value, the finding will usually say the repair does not make sense against a new unit, and we say so before the visit if you tell us the model.

When to book

Be honest with yourself about the unit first. A built-in, drawer or over-the-range microwave is installed into cabinetry, is often part of a matched suite, and costs enough that a magnetron or door-switch repair is frequently the sensible choice; book those. A basic countertop microwave often costs less to replace than a diagnostic plus parts, and we will tell you that up front rather than send a technician. If you send us the model number, we will say which side of that line it falls on. When a visit does make sense, the diagnostic is $89, waived if you proceed, and the finding gives the repair figure against a replacement. See microwave repair.

Questions

Related

• Oven not heating
• Microwave
• GE
• Whirlpool
• LG
• Samsung
• KitchenAid
• Frigidaire
• Bosch