Microwave displays H0 or HO and does not heat, though lights and fan may operate.
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: The magnetron and high-voltage circuit operate at extremely dangerous voltages. Do not attempt to service these components unless you are a trained technician. Always unplug the microwave before any inspection.
User-level checks:
- Confirm that the unit is not in demo mode (if applicable) by checking the user manual and disabling demo mode.
- Try heating a cup of water for 1–2 minutes. If the timer counts down, light and fan run, but the water stays cold and H0 appears, discontinue use.
Technician-level actions:
- Remove the cabinet and inspect the high-voltage transformer, capacitor, diode, and magnetron for visible damage or burning.
- Test each high-voltage component with appropriate procedures and safety equipment.
- Replace the failed component(s), typically the magnetron or high-voltage transformer, using Commercial Chef-compatible parts.
Recommendation: For most homeowners, replacement of the entire microwave is more practical and safer than high-voltage repair. Contact a professional if you wish to repair rather than replace.