E09
Thermador
Stuck Relay / Power Relay Failure on Control Board
Microwave shows E09 and beeps; interior light may stay on and fan may run.
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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
Welded relay contacts on main control,Control board component failure,Shorted load causing relay damage,Power surge damage
How to Fix / Troubleshooting
Safety first: Disconnect power immediately if the microwave behaves abnormally (runs with door open, will not stop, etc.).
- Step 1 – Power reset: Unplug or switch off the breaker for 10 minutes. Restore power and see if E09 clears.
- Step 2 – Observe behavior: If the unit starts by itself or certain functions remain on, a relay may be stuck.
- Step 3 – Inspect control board (qualified persons): Remove the control panel and examine the main PCB for burn marks, cracked solder joints, or damaged relays.
- Step 4 – Replace control board: Because relays are not typically serviced individually in home environments, replace the entire main control board with a Thermador OEM part.
Warning: Do not continue using the microwave with a suspected relay fault; it can be a fire hazard.
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Repair Difficulty
Hard
4/5
Required Part
Main Control Board
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