HVAC Code Lookup

Lennox Furnace Code 1

WarningShown as: 1 rapid flash (1/2 second on, 1/2 second off), then the LED stays off for 3 seconds and repeats

The 120-volt line power feeding the furnace has hot and neutral reversed. The SureLight control senses line polarity and will not run the burners until the polarity is correct.

Manual wording: “1 - Reverse Line Voltage Polarity”

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

Likely causes, most common first

  1. Hot and neutral wires reversed at the furnace junction box
  2. Reversed polarity in the branch circuit or receptacle feeding the furnace

What you can safely check yourself

  • Confirm the furnace disconnect switch and the breaker feeding the furnace are on
  • Turn the furnace power switch off for 30 seconds and back on once to see whether the code returns

When to call a technician

Correcting line voltage polarity means working inside the furnace junction box or the branch circuit. This is a licensed electrician or HVAC technician job.

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

Sources

Other Lennox codes