Lennox Error Code LED#1-Off, LED#2-Slow Flash

Possible cause: 3.2.1 Miswiring of furnace or improper con- nections to combustion air blower. Corresponding action/comments: ACTION 1 − Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections. Possible cause: 3.2.2 Pressure switch stuck closed. Corresponding action/comments: ACTION 1 − Check that the pressure switch is open without the combustion air blower operat- ing. Replace if malfunctioning

Possible cause: 3.3.1 Miswiring of furnace or improper con- nections to combustion air blower. Corresponding action/comments: ACTION 1 − Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections. Possible cause: 3.3.2 Combustion air blower failure. Corresponding action/comments: ACTION 1 − If there is 120V to combustion air blower and it does not operate, replace combus- tion air blower.

Possible cause: 4.1.1 Pressure switch does not close due to incorrect routing of the pressure switch lines. Corresponding action/comments: ACTION 1 − Check that the pressure switch lines are correctly routed. Correctly route pressure switch lines. Possible cause: 4.1.2 Pressure switch does not close due to obstructions in the pressure lines. Corresponding action/comments: ACTION 1 − Remove any obstructions from the the pressure lines and/or taps. Possible cause: 4.1.3 Pressure switch lines damaged Corresponding action/comments: ACTION 1 − Check pressure switch lines for leaks. Replace any broken lines. Possible cause: 4.1.4 Pressure switch does not close due to a low differential pressure across the pressure switch. Corresponding action/comments: ACTION 1 − Check the differential pressure across the pressure switch. This pressure should exceed the set point listed on the switch. ACTION 2 − Check for restricted inlet and ex- haust vent. Remove all blockage. ACTION 3 − Check for proper vent sizing and run length. See installation instructions. ACTION 4 − Check voltage to thre combustion air blower. Possible cause: 4.1.5 Wrong pressure switch installed in the unit, or pressure switch is out of calibration. Corresponding action/comments: ACTION 1 − Check that the proper pressure switch is installed in the unit. Replace pressure switch if necessary. Possible cause: 4.1.6 Miswiring of furnace or improper con- nections at pressure switch. Corresponding action/comments: ACTION 1 − Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections. Possible cause: 4.1.7 Pressure switch failure. Corresponding action/comments: ACTION 1 − If all the above modes of failure have been checked, the pressure switch may have failed. Replace pressure switch and determine if unit will operate.

Possible cause: 6.1.1 Low pressure differential at the pres- sure switch. Corresponding action/comments: ACTION 1 − Check for restricted vent inlet or ex- haust. Remove all blockage. ACTION 2: Check for proper vent sizing. See installation instructions.