Lennox Ducted Heating

Lennox Ducted Heating Error Code 3 Flashes

Ducted Heating

3 Flashes means different things on different Ducted Heating models. Enter your model number to see only your reading, or find your model below.

What It Means

  • ML196UHE: Burner failed to light, or lost flame during heat demand
  • G24M: Combustion Air Prove Switch Open
  • ML180UH: Pressure switch open with combustion air inducer energized.
  • ML296UHV: Pressure switch open with inducer energized
  • TUA*S(N,L)(A,S)F: Combustion air inducer proving switch failed closed before CAB is energized or failed open after CAB is energized
  • LF24: Pressure switch failed closed before CAI is energized or failed open after CAI is energized

Causes & actions from Lennox

Burner failed to light, or lost flame during heat demand

Models: ML196UHE

How it shows
  • Integrated control red LED: 3 Flashes

This manual entry does not list further causes or actions.

Applicable models & manual sources

Combustion Air Prove Switch Open

Models: G24M

How it shows
  • a3 diagnostic led: 3 Flashes

Combustion Air Blower: On Gas Valve: Off Supply Air Blower: On

Applicable models & manual sources

Pressure switch open with combustion air inducer energized.

Models: ML180UH

How it shows
  • integrated control single led: 3 Flashes

Pressure switch open with combustion air inducer energized.

Applicable models & manual sources

Pressure switch open with inducer energized

Models: ML296UHV

How it shows
  • Integrated control red LED: 3 Flashes

This manual entry does not list further causes or actions.

Applicable models & manual sources

Combustion air inducer proving switch failed closed before CAB is energized or failed open after CAB is energized

Models: TUA*S(N,L)(A,S)F

Unit heater (indoor)

How it shows
  • integrated control single led: 3 Flashes

This manual entry does not list further causes or actions.

Applicable models & manual sources
  • TUA*S(N,L)(A,S)F

    Combustion air inducer proving switch failed closed before CAB is energized or failed open after CAB is energized

    TUA*S(N,L)(A,S)F manual, page 17

Pressure switch failed closed before CAI is energized or failed open after CAI is energized

Models: LF24

How it shows
  • integrated control single led: 3 Flashes

Pressure switch failed closed before CAI is energized or failed open after CAI is energized

Applicable models & manual sources
  • LF24

    Pressure switch failed closed before CAI is ener- gized or failed open after CAI is energized

    LF24 manual, page 14

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 →