Lennox E270 Error Code

What does Lennox E270 mean?

E270 is a soft lockout triggered after the furnace has exceeded the maximum number of ignition retry attempts without establishing a flame. The IFC logs E270 and enters Watchguard mode for approximately one hour before allowing another ignition attempt. Root causes include gas supply interruptions, a failed or mispositioned hot surface ignitor, a dirty flame sensor that does not confirm ignition quickly enough, or an ignitor that lights the burner but loses flame before the sensor can confirm.

Symptoms

• Furnace enters Watchguard mode — no heat produced for approximately one hour.
• E270 alert displayed on thermostat or control board after multiple failed ignition attempts.
• Inducer and ignitor cycle repeatedly before the lockout occurs.
• No flame visible at the burners during the ignition trial.

Common causes

• No gas reaching the burner due to a closed manual shutoff valve, empty propane tank, or gas supply interruption.
• Failed or cracked hot surface ignitor unable to reach ignition temperature.
• Mispositioned ignitor not aligned with the gas stream from the burner ports.
• Dirty or contaminated flame sensor not confirming flame quickly enough, causing premature gas valve shutoff.
• Low gas pressure at the manifold preventing proper flame establishment.

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Diagnostic steps

1. Verify gas supply is on and flowing

   Confirm the manual gas shutoff valve at the furnace is fully open. If the unit uses propane, check tank level. Attempt to light a gas appliance elsewhere in the building to confirm gas supply.

2. Wait out the Watchguard period or perform a manual reset

   Allow the one-hour Watchguard period to expire, or power cycle the furnace (disconnect off for 30 seconds) to clear the lockout and allow a fresh ignition attempt.

3. Inspect and test the hot surface ignitor

   Measure ignitor resistance — replace if open or outside the 39–70 ohm range. Verify the ignitor is positioned correctly in the burner port alignment and is not contacting the burner assembly.

4. Clean the flame sensor

   Lightly abrade the flame sensor rod with fine steel wool to remove the oxide layer, improving the sensor's ability to confirm flame quickly and prevent premature shutdown.

5. Measure manifold gas pressure

   Check manifold gas pressure with the burners running and compare against the SL280DFNV nameplate rated pressure. Low pressure prevents proper flame establishment.

When to call a professional

If E270 returns after confirming gas supply, cleaning the flame sensor, and inspecting the ignitor, the gas valve or IFC board may be at fault. Gas pressure adjustment and gas valve testing require a licensed technician with a calibrated manometer and gas-safe tools. Repeated E270 faults can damage the ignitor from repeated thermal cycling.