Microwave displays F4 and may shut down during operation.
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: An open thermostat indicates an overheat condition or failed safety device. Unplug the microwave and do not use it until inspected.
- Allow full cooling: Let the unit cool for at least 1 hour.
- Inspect thermostats:
- Remove the outer cabinet.
- Locate thermostats on the magnetron and cavity.
- Check for physical damage or discoloration.
- Replace open thermostat: Using a multimeter (if qualified), test continuity. Replace any open thermostat with the exact Black+Decker-specified part.
If F4 returns after thermostat replacement, the magnetron or cooling system may be defective and should be evaluated by a technician.
Repair Difficulty
Required Part
We may earn a commission from links on this page.