I recently purchased a house that has a carrier furnace. House has been vacant two years. I am getting a code of reverse polarity. I have reversed the leads both line 1 and line 2. I have also reversed the secondary leads. I have disconected all of the components on the board, inducer motor,fan,ignitor, and the high limits , and air swiches. Still have the blinking light. I am stumped. All works well on the Air conditioner side but all that controls is to turn compressor and fan on. I have also replaced the thermastat, and also the board disconnected. A new board is 250 plus and I dont want to replaced unless necessary. All connections on back of the board look good no burned spots .Any help appreciated.