it started out as it would have a hard time lighting it would take 3 or 4 cycles then it went to lighting for a few seconds then turning off the burners and go into watchguard mode. so i cleaned the flame sensor this seemed to fix it for a few heating cycles. i then replaced the flame sensor, now i get nothing not even opening the gas valve. so i switched back to the old sensor and it tries to light but wont stay lit. so i checked the pressure switch it is working i cleaned the hose and the condensation tube. now here is where i get confused, with the old flame sensor in i can jump the gas valve manually when the ignitor is at full temp and get it to light and stay lit with the jump, if i leave the jump on for 3 or 4 min. then remove it the furnace will stay lit in normal operation. if i shut it down and re start a few min later it will run normal operation, but if i leave it for 20 min. i will revert back to the symtoms above. with the new sensor in i cannot jump the gas valve and keep the fans on they shut off and the leds tell me the board is wired wrong. help please.