Lennox Error Code 114 — Causes & Fix

What this code means

Lennox error code 114 indicates an ignition failure lockout — the furnace attempted to ignite the burner but the flame sensor did not detect a flame within the trial-for-ignition period. After a set number of failed ignition attempts (typically 3 retries), the furnace locks out on code 114. This appears on Lennox G61MP, XC17, and other models with a digital control board display. The furnace will not attempt ignition again until manually reset. Code 114 is one of the most common Lennox service calls.

Common Causes

• Failed hot surface igniter (HSI) — The silicon carbide or silicon nitride igniter has cracked or worn to the point where it no longer reaches ignition temperature (approximately 1800°F). This is the most common hardware cause of code 114.
• Dirty or failed flame sensor — Even if ignition occurs, a coated or corroded flame sensor rod won’t detect the flame and the gas valve closes, causing code 114 to log.
• No gas supply or low gas pressure — A closed shutoff valve, low supply pressure, or a gas valve that fails to open prevents combustion from occurring.
• Draft/pressure switch fault preventing gas valve opening — If the pressure switch hasn’t confirmed adequate draft before the ignition trial, the gas valve won’t open and code 114 results.

Step-by-Step Fix

1. Visually inspect the igniter — Power off the furnace and locate the hot surface igniter (a fragile ceramic element in the burner assembly). Look for cracks, a broken element, or discoloration from a prior failure. Handle only by the lead wires — never touch the ceramic.
2. Test the igniter electrically — With the furnace off, disconnect the igniter leads and measure resistance across them. A healthy Lennox igniter reads 40–90 ohms. Open circuit (OL) = failed igniter requiring replacement.
3. Clean the flame sensor — Remove the flame sensor rod (one screw) and lightly clean the rod with fine emery cloth to remove carbon buildup. Reinstall and test.
4. Confirm gas supply — Verify the gas shutoff valve at the furnace is fully open and other gas appliances in the home are working. Listen for the gas valve click during an ignition attempt.
5. Reset and observe — Press the furnace’s manual reset button (or cycle the breaker) and initiate a heat call. Watch and listen: igniter should glow orange/red within 15–30 seconds, then the gas valve opens and the burner lights. If gas lights but shuts off quickly, clean the flame sensor.

Parts Often Needed

When to Call a Pro

If the igniter glows, gas is confirmed, and code 114 persists after cleaning the flame sensor, the gas valve’s opening pressure or the pressure switch may require adjustment — tasks that require a licensed HVAC technician with gas certification.