then it is the main blower or the control board theyt some times short outn the contacts and will not let the blower run power the blower with jumper and see if it runs
when the light is blinking 4 times is the main blower running is there forced air comming from vents if not it could be the control board or the blower motor you would need to test the blower motor by by passing the control board
When was the last you replaced the air filters if they are pluged you will not have athe right of return air and will trip high limit and if it trips often it will stay open