E18
Siemens High-Voltage Safety Interlock Fault

Microwave shows E18 and does not heat, though light and turntable may operate.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Blown internal safety fuse in high-voltage circuit, defective high-voltage relay on control board, shorted high-voltage diode, magnetron short to chassis

How to Fix / Troubleshooting

Critical safety warning: High-voltage components can be lethal. Do not attempt to access or replace internal fuses, relays, or HV parts unless you are a trained technician.

User-level checks:

  • 1. Confirm symptom: Place a cup of water inside and run for 1–2 minutes. If the water stays cold and E18 appears, heating has failed.
  • 2. Power reset: Unplug for 5 minutes, then reconnect. If E18 returns immediately, an internal safety device has likely opened.

Internal diagnosis involves testing the high-voltage fuse, diode, capacitor, and magnetron. This must be done by a Siemens-authorized technician.

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Repair Difficulty

Professional Required 5/5

Required Part

High-Voltage Fuse / High-Voltage Diode
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