HVAC Code Lookup

Lennox Furnace Code 8

Safety faultShown as: 8 rapid flashes (1/2 second on, 1/2 second off), then the LED stays off for 3 seconds and repeats

The flame rollout switch is open. This safety switch trips when flame or hot combustion gas escapes the burner box instead of going up the heat exchanger.

Manual wording: “8 - Rollout Switch Open”

Documented for: ML180UHE, ML193UHE and other Lennox furnaces using SureLight integrated control 103217-03 or 107163-01

Likely causes, most common first

  1. Blocked or restricted vent or flue
  2. Combustion air inducer not moving enough air
  3. Cracked or plugged heat exchanger
  4. Blocked burners or misaligned burner flames

What you can safely check yourself

  • Check the outdoor intake and exhaust pipes for snow, ice, leaves or nesting debris
  • Check the air filter and replace it if it is dirty

When to call a technician

A tripped rollout switch means combustion gas went where it should not. Do not reset the rollout switch and do not run the furnace. Shut the furnace off and have a technician inspect the vent, inducer and heat exchanger before it runs again. If you smell gas, leave the house and call the gas utility.

A Lennox furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.

Sources

Other Lennox codes