If the turntable moves and the display looks normal but food stays cold, the magnetron circuit is not producing useful microwave energy. The failure cluster is small, but the voltages inside the appliance are not.
Typical Causes
- Door interlock switches that do not prove “closed” to the control board
- Blown thermal or line fuses after surges or vent issues
- High-voltage diode or capacitor problems feeding the magnetron
- End-of-life magnetron on well-used units
Safety
Capacitors can retain lethal charge unplugged. Unless you are trained on HV discharge and testing, leave internal repair to qualified technicians.
Repair vs. Replace
Built-in and over-the-range models carry installation cost. Many repairs are economical compared with full replacement—especially switch and fuse-level faults—when performed with correct parts.