Microwave runs but does not heat and displays E3
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.
Possible Causes
How to Fix / Troubleshooting
Critical safety warning: High-voltage components inside a microwave (transformer, capacitor, diode, magnetron) can deliver lethal shocks even when unplugged. Do not attempt HV testing or replacement unless you are trained and equipped to safely discharge the capacitor. For most users, this is a technician-only repair.
Basic user checks (no cabinet removal):
- 1. Confirm symptom: Place a cup of water inside and run for 1–2 minutes. If the turntable rotates and the light is on but the water remains cold and E3 appears, heating has failed.
- 2. Check power supply: Ensure the outlet is properly grounded and not on an overloaded circuit. Avoid using extension cords.
- 3. Reset power: Unplug the microwave for 5–10 minutes to reset the control board. Plug back in and test again.
Technician-level checks (for professionals only):
- Discharge the high-voltage capacitor safely using a resistor and insulated tools.
- Test the high-voltage diode and capacitor with appropriate test methods.
- Check the magnetron for continuity and signs of arcing or burning.
- Inspect the high-voltage transformer for overheating or open windings.
Recommendation: If E3 persists after a power reset, contact an authorized Daewoo service center. Replacing magnetron or HV components requires specialized skills and parts.