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

Possible cause: 5.1.1 Check that gas is being supplied to the unit. Corresponding action/comments: ACTION 1 − Check line pressure at the gas valve. Pressure should not exceed 13" WC for both natural and propane. Line pressure should read a minimum 4.5" WC for natural and 8.0"WC for propane. Possible cause: 5.1.2 Miswiring of gas valve or loose con- nections at multi−pin control amp plugs or valve. Corresponding action/comments: ACTION 1 − Check for correct wiring and loose connections. Correct wiring and/or replace any loose connections. Possible cause: 5.1.3 Malfunctioning gas valve or ignition control. Corresponding action/comments: ACTION 1 − Check that 24V is supplied to the gas valve approximately 35 seconds after heat demand is initiated. ACTION 2 − Replace the valve if 24V is supplied but valve does not open (check for excessive gas line pressure before replacing gas valve). ACTION 3 − Replace the control board if 24V is not supplied to valve.

Possible cause: 6.2.1 Sensor or sense wire is improperly installed. Corresponding action/comments: ACTION 1 − Check that sensor is properly lo- cated (page 10) and that the sense wire is properly attached to both the sensor and the control. Possible cause: 6.2.2 Sensor or sense wire is broken. Corresponding action/comments: ACTION 1 − Check for a broken sensor. ACTION 2 − Test continuity across the sense wire. If wire or sensor are damaged replace the component. Possible cause: 6.2.3 Sensor or sensor wire is grounded to the unit. Corresponding action/comments: ACTION 1 − Check for resistance between the sensor rod and the unit ground. ACTION 2 − Check for resistance between the sensor wire and the unit ground. ACTION 3 − Correct any shorts found in circuit. Possible cause: 6.2.4 Control does not sense flame. Corresponding action/comments: ACTION 1 − Check the microamp signal from the burner flame. If the microamp signal is be- low 0.70 microamps, check the sense rod for proper location or contamination. ACTION 2 − Replace, clean, or relocate flame sense rod. If rod is to be cleaned, use steel wool or replace sensor. DO NOT CLEAN ROD WITH SAND PAPER. SAND PAPER WILL CONTRIBUTE TO THE CONTAMINATION PROBLEM. NOTE: Do not attempt to bend sense rod.

Possible cause: 6.4.1 Recirculation of flue gases. This con- dition causes rough ignitions and op- eration. Problem is characterized by nuisance flame failures. Corresponding action/comments: ACTION 1 − Check for proper flow of exhaust gases away from intake vent. Remove any ob- stacles in front of the intake and exhaust vent which would cause recirculation. ACTION 2 − Check for correct intake and ex- haust vent installation. See instructions Possible cause: 6.4.2 Improper burner cross−overs Corresponding action/comments: ACTION 1 − Remove burner and inspect the cross−overs for burrs, or any restriction or if crossover is warped. Remove restriction or re- place burners.

Possible cause: 6.5.1 Loose sensor wire connection causes intermittent loss of flame sig- nal. Corresponding action/comments: ACTION 1 − Check that the sensor is properly lo- cated. ACTION 2 − Check that the sense wire is proper- ly attached to both the sensor and the control. Pay extra attention to the pin connectors.