Lennox Ducted Heating

Lennox Error Code LED #1 Slow Flash / LED #2 ON

Ducted Heating:

What It Means

  • Primary/secondary limit CLOSED? NO: gas valve de-energized, combustion inducer de-energized, indoor blower ON until switch closes. LED1 SLOW flash AND LED2 ON. Failed limit-reset branch enters limit Watchguard: gas valve/inducer OFF, indoor blower OFF with delay;60minute reset. Table2 board limits:63K8901/24L85 limit must close within5ignition trials;56L83/97L48 must close within3minutes. Keep board conditions distinct.

Causes & actions from Lennox

How it shows
  • SureLight board LEDs (DS1/DS2): LED #1 Slow Flash / LED #2 ON (led1: flashing (slow), led2: on)

Primary or secondary limit switch open. Gas valve de-energized, combustion air inducer de-energized, indoor blower on until switch closes. Also indicates Limit Switch Watchguard mode (gas valve off, comb. air inducer off, indoor blower off with delay).

Applicable models & manual sources
  • G24M

    Primary/secondary limit CLOSED? NO: gas valve de-energized, combustion inducer de-energized, indoor blower ON until switch closes. LED1 SLOW flash AND LED2 ON. Failed limit-reset branch enters limit Watchguard: gas valve/inducer OFF, indoor blower OFF with delay;60minute reset. Table2 board limits:63K8901/24L85 limit must close within5ignition trials;56L83/97L48 must close within3minutes. Keep board conditions distinct.

    G24M manual, page 28

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

What should you check next?

Continue in ACLogics with guided diagnosis for your equipment and symptoms.

Download on the App Store Get it on Google Play
Scan to install on your phone Free · iPhone & Android
See how guided diagnosis works →