Im getting a twinning error code on the furnace. I just replaced the board and had to use the wiring diagram on the unit to install the new board, because someone removed the old one and through it away. I have reversed polarity on secondary 24v and main power, also checked it with a meter it's rite. I double checked the wiring to the board and found no problem, any suggestions would be appreciated.

Thanks, Mike

Reverse the wires on the primary side of the transformer.