Tried replacing the door switch first, as that is one of the most common problems and relatively cheap to fix (not cheap labor, though!) When that didn't work, I diagnosed other possible problems using my DMM and the schematic provided with the machine. None of the potential problems was a cause, leaving the main control board as the only possible problem. Main control board arrived quickly, and installed easily and quickly. It required setup, which was listed on the schematic sheet. Now works as designed.