Hi all. Hayward H400 heater 15 years old but seemingly in good condition. Had several bouts with the display and control PCBs. Current situation is new board and dislplay. New Ignitor and new 5" Flame sensor. Blower comes on, gas comes on and heat light comes on for about 3-5 secs and then shuts off. 3X and provides IF error code. I pulled the ignitor and it gets energized and red hot. I cleaned out all spider webs from orifices and I smell gas as it starts up. I don't here the whoosh of the flame up from the burners and it fails to light. The valve regulator adjustment screw is all the way in which I believe is max flow for the valve.
Thoughts? Thank you for any advice!