The 208427AC does not require an air flow sensor. This power supply runs as soon as 120v is applied. Used in an F50E that is wired to the furnace blower or through a sail switch.
This power supply has been configured for use in a power box without the air flow sensor. The animated photo below shows a power box with and without the air flow sensor.
Honeywell has disabled the air flow sensor feature by cutting the jumper J8. Restoring the jumper will allow the use of an air flow sensor. If your F50A-F50E power box has the air flow sensor and it is needed, then you need to replace the complete power box with the 208420A.