F04 indicates a fault in the heating circuit.
It can be a main board, wiring, thermostat or heater fault.
You would need to check the heater and thermostats with a multimeter to ensure they are not open circuit.
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However, the first thing to try is a reset of the control board.
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Turn the dial to off.
Turn the dial clockwise to the 6 o'clock position.
Press the start button 3 times
Turn the dial 1 position clockwise.
Press the start button 3 times.
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This should erase the code.
Try the machine again.
If the code comes back, you need to check out the heating circuit.
If you change or repair any part, reset the board, then try again.
Daynah
April 2014