Originally Posted by bausin
I was looking at a neighbor's furnace and saw no LED lit through the viewing hole nor after I took the panel off. I ordered him a new board but then got to wondering if the door switch had been open the whole time (there were three screws missing on the panel). The fan was running before and after I removed the panel. So it's good to know I didn't order a board for nothing. I'll have to check that door switch when I replace the board.
Yeah if the fan was running after you took the door off then someone probably wired around the switch or taped it permanently closed. Because the door switch should turn everything off.
This is why you should never trust a door switch to kill power, always verify power is off. I've been shocked several times because of that or someone wiring the nuetral leg to the door switch instead of hot.