I am posting this again since there are probably a lot of Techs out there who are new to this site.
IF YOU ARE REPLACING ANY OF THE OLDER BOARDS IN A YORK FURNACE WITH THE NEW REPLACEMENT BOARDS:
S1-33102956000 SINGLE STAGE BOARD
S1-33102954000 2-STAGE PSC MOTOR BOARD
S1-33102977000 2-STAGE VARIABLE SPEED MOTOR
AND YOU GET A FAULT CODE 9 ON THE NEW CONTROL –REVERSE THE 2 WIRES ON THE SECONDARY SIDE OF THE TRANSFORMER (R & C), RECYCLE THE POWER AND THE FAULT CODE SHOULD CLEAR.
When replacing an older variable speed motor CFM programming board with the new combination board (has both the ignition control and CFM programming board combined into one control) you will need to order a wiring harness S1-02541103000.
Hopefully this information will assit you in solving the Fault Code 9 — reversed polarity — on a replacement board. Keep in mind that, both reversed line voltage polarity and an improper ground can also cause this but if you have checked and verified that those are correct, then reverse the secondary side of the transformer and the fault code should clear.