Display shows F11, F12, or F13
Boiler shows absolutely no display or lights at all
Radiator is warm at the bottom but stays cold across the top
Door won't lock so the cycle can't start, or won't unlock after the cycle finishes
Display shows OE, UE, or IE
Rattling or buzzing noise from the dehumidifier during use
"Tank full" light comes on and the unit stops, even though the tank isn't actually full
Visible ice or frost forming on the internal coils
Dehumidifier is running but the water tank stays empty
Toast comes out browned unevenly, or noticeably darker on one side