Can anyone solve this problem with my whrilpool f/f

Hi my American style whrilpool fridge freezer model number s20d rbb32-a/g has a strange problem the display on the lcd panel shows that the door to the freezer is open and the warning alarm sounds even with the door closed.I have checked the door switch in the freezer and it works perfectly i even swapped it with the fridge one to make sure all was ok. Someone advised me that it was the rear pcb and that it would need changed but lucky enough my brother has the exact same f/f and i swapped over his pcb with mine and the problem did not show up on his display and every thing worked fine so that saved me spending £150 on something i did not need. The strange thing is when you press the door switch the light dims down but does not go out i even traced the wires from the switch back to the pcb and disconnected them sure enough the lights went out but the display still shows the door open and sounds the alarm. Before all this started i was having a problem with the ice maker because the water still dripped threw the pipe in to the already full tray spilling over and freezing ice all over everything.At this time i noticed a burning smell from the ice dispencer so switched the ice maker off shortly after this the door problem started.After thinking about this today i disconnected the ice maker and tried switching the f/f on again but it still shows the door problem with the alarm.
Can anyone help me with what to try next ? Or has anyone had similar problems?