Microwave shows E4 and stops heating; turntable and light may still work.

Safety first: Unplug the microwave. Internal components can be dangerous.

User-level checks:

• Ventilation: Ensure vents are not blocked and the unit has proper clearance. Clean grease and dust from vents.
• Cool-down: Allow the microwave to cool for at least 30 minutes, then plug in and test with a short 30-second run.

Technician-level checks:

• Remove the outer cabinet (unplugged). Locate the cavity temperature sensor / thermistor, usually clipped to the top or side of the cooking cavity.
• Inspect the wiring harness and connector for burns or loose contacts.
• Measure resistance of the thermistor at room temperature and compare with Clatronic specifications. Replace if open, shorted, or out of range.
• If the thermistor is good, the fault may be on the control PCB temperature input circuit.

Warning: If you are not trained, do not attempt internal measurements. Contact a qualified technician.