The control system has detected open contacts at the Blocked Intake air pressure switch – inadequate supply of intake (combustion) air.
If the water heater has been installed as a conventional vent appliance – Ensure the intake air connection screen is not clogged with debris. See Service Notes – Venting on page 7.
If water heater has been installed as a direct vent appliance – check for restrictions, too many equivalent feet, or too many elbows in the intake air piping. Review venting installation section of the Instruction Manual that came with the water heater – see Table 1 on page 7 in this manual. Ensure the vent/intake air piping has been installed within manufacturers requirements.
If water heater has been installed as a direct vent appliance – temporarily disconnect the intake air pipe at the blower connection on the water heater – ensure the screen inside the intake air connection was removed during installation. See the Service Notes for venting on page 7.
Check all wiring between the Blocked Intake air pressure switch and the CCB’s J6 Socket (page 36) pins 4 & 14. Perform close visual inspection of the pins inside the plug and socket – ensure plugs and sockets are mating properly and providing good contact. Repair/replace anything worn or damaged.
Review the air pressure switch information beginning on page 18. Perform the pressure switch test procedure for the Blocked Intake air pressure switch – see pages 21 through 23. Replace the Blocked Intake switch if defective. Call the technical support phone number shown on the water heater labeling for further assistance if the problem has not been corrected after performing the procedures outlined here.