I have a York YP9C modulating furnace and matching York Affinity 8T 4 ton 2-stage condensing unit. The units are working wonderfully with no problems in the cooling mode. I have not used it for heating yet, so I do not know how it works in the heating mode. The furnace fault light shows a green slow steady blink when the thermostat is not calling for cold. I understand that this code means normal operation. When the thermostat calls for cold and the condenser starts and the furnace ECM motor starts ramping up, the green light increases its blinking frequency and an additional amber light showing a slow steady blink appears. My understanding is that this code means this is normal operation with a call for heat.

My question is: Is this normal or could there be a fault in the thermostat wiring? If it is normal, how can there be a call for heat, when the thermostat is set to cool mode? I did try changing the thermostat to dual mode (heat or cold) which made no difference in the fault codes.

I suggest you contact the professional that installed the unit. The working of the York system are NOT USER FRIENDLY!

BTW if there was a fault in the thermostat wiring the unit would not work at all.

I am working on a control board from a york system the board is a #031-01972-000 it is showing an error code four green flashes...

I am working on a York system with a control board no#031-01972-000 pushing the error button it is indictating four green flashes and is missing that information panel...

That was real helpful. Usually when you take the door off the bottom where the blower motor is there is a little chart with what the codes mean, Any heating cooling contractor can tell you that