Lennox error codes
This page lists the fault codes this brand documents, with likely causes and a short repair path. The codes apply to model numbers such as ML180UHE; check the label on your unit to confirm yours.
12 codes across 1 appliance type.
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Lennox furnace codes
1 FlashReverse line voltage polarity or phasing of 120V power2 FlashesImproper earth ground3 FlashesBurner failed to light, or lost flame during heat demand4 FlashesLow flame signal, check flame sensor5 FlashesWatchguard: burner failed to light, exceeded maximum retries or recycles (1 hour lockout)7 FlashesPrimary or secondary limit switch open, or Watchguard: limit open longer than 3 minutes8 FlashesRoll-out switch open9 FlashesPressure switch failed to close or opened during heat demand, inducer on10 FlashesWatchguard: pressure switch opened 5 times during a single heating demand11 FlashesPressure switch stuck closed before the combustion air inducer starts12 FlashesFlame sensed without gas valve energized13 FlashesLow line voltage