I have a gas boiler(crown, aruba X3 unit) I am trying to determine if my S86F circuit board is gone; or my air pressure switch is gone. The unit will start up and go real strong for about 8to10 minutes, and then it switch off gas burner and on the burner again; it will do this for some time and hold on run; then kick out again, and eventually shut off. It heats fine; but what the blazeses is wrong? The unit is 20 years old, the S86F board has never been changed, the air pressure switch has.:confused:

Is a control sensor telling the boiler to shut off. IE hi limit or water temp control?