My heat unit will not kick on but my a\c will. The red light on my circuit board flashes four times then pauses then does it again etc.. It is a york central heat\air unit model #DCRAF036N090A SERIAL#NHDM075154

I need to know the ton of my unit model#d3cgo4n06225c

The blower will not come on when I turn on the heat and the heat sensor keeps tripping the relay switch. Can you tell me what I need to do?