Microwave shows E3 and will not heat; fan may run briefly then stop.

Safety first: Unplug the microwave. The high-voltage system (transformer, capacitor, diode, magnetron) is extremely dangerous. Discharging the capacitor incorrectly can cause serious injury. If you are not trained, call a professional.

• Check ventilation: Ensure all external vents on the Ambiano microwave are clear of obstructions. Do not operate the unit in a confined cabinet without proper clearance.
• Inspect cooling fan: Remove the outer cover and visually inspect the cooling fan motor and blades. Spin the fan by hand (with power disconnected) to ensure it moves freely and is not obstructed by debris.
• Check magnetron thermal cut-out (TCO): Locate the thermostat/thermal fuse mounted on or near the magnetron. Test for continuity with a multimeter. If open, it may have tripped due to overheating and must be replaced (do not bypass).
• Inspect magnetron: Look for burn marks, cracks, or a burnt smell around the magnetron. If the magnetron is visibly damaged or the TCO repeatedly opens, the magnetron is likely failing and should be replaced with a compatible Ambiano magnetron assembly.

Warning: Do not attempt to test the high-voltage circuit live. Magnetron and HV components should only be serviced by qualified personnel.