Lennox Ducted Heating

Lennox Error Code LED #1 OFF / LED #2 SLOW FLASH

Ducted Heating:

What It Means

  • Initial pressure OPEN? NO branch: gas valve OFF, combustion air blower OFF, indoor blower OFF with delay; source response says hold until pressure switch CLOSES or thermostat resets control, despite question asking OPEN. Later pressure CLOSED within2.5minutes? NO: pressure Watchguard, same OFF/SLOW pattern and equipment outputs;5minute reset then retry. Retain original contradictory initial question/response and separate Watchguard branch.

Causes & actions from Lennox

How it shows
  • SureLight board LEDs (DS1/DS2): LED #1 OFF / LED #2 SLOW FLASH (led1: off, led2: flashing (slow))

Combustion air pressure switch not open initially, or pressure switch failed to close in 2.5 minutes and entered Watchguard mode. Gas valve off, combustion air blower off, indoor blower off with delay.

Applicable models & manual sources
  • G24M

    Initial pressure OPEN? NO branch: gas valve OFF, combustion air blower OFF, indoor blower OFF with delay; source response says hold until pressure switch CLOSES or thermostat resets control, despite question asking OPEN. Later pressure CLOSED within2.5minutes? NO: pressure Watchguard, same OFF/SLOW pattern and equipment outputs;5minute reset then retry. Retain original contradictory initial question/response and separate Watchguard branch.

    G24M manual, page 27

Disclaimer: This information is for general reference. Code wording and instructions vary by model. Always follow the service manual for your exact unit.

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