Quick answer: Lennox code 270 (E270) means the furnace tried to light the maximum number of times without sensing a flame, so it went into a soft lockout. The usual causes are a dirty flame sensor, a failing ignitor, a gas supply problem or a gas valve issue. The furnace will typically try again automatically after the lockout period.
Safety first: if you smell gas, do not reset or relight anything. Leave the home and call Nicor Gas at 1-888-642-6748 or 911 from outside.
What Does Lennox Error Code 270 Mean?
Lennox describes code 270 as soft lockout: exceeded maximum number of retries, no flame current sensed. Each time the furnace calls for heat, it heats the ignitor, opens the gas valve and checks for flame with the flame sensor. If it never senses flame after several tries, it locks out to prevent unburned gas from building up.
Common Causes of Code 270
- A dirty flame sensor. A thin coating on the sensor rod is one of the most common causes of no-heat calls.
- A weak or failed hot surface ignitor (related codes: 207 and 290).
- Gas supply problems: the gas valve at the furnace turned off, low gas pressure, or a utility issue.
- A failing gas valve.
- Poor ground or reversed polarity that prevents the control from reading the flame signal.
Safe Checks You Can Do First
- Make sure the gas is on. The handle on the gas line next to the furnace should be parallel to the pipe. Check that other gas appliances, like the stove or water heater, are working.
- Check the furnace switch and breaker are on.
- Restart once by turning the furnace switch off for 30 seconds and back on, then watch whether the burners light.
If you smell gas, do not restart the furnace. Leave the home and call Nicor Gas at 1-888-642-6748. Do not remove or sand the flame sensor yourself; it requires removing furnace components near the burners.
What a Technician Will Check
We measure flame current, clean or replace the flame sensor, test the ignitor, check inlet and manifold gas pressure, test the gas valve and verify grounding and polarity. Many code 270 calls are fixed on the first visit with parts from our truck. Emergency calls usually get a technician within one to three hours.
Seeing a Lennox code in the Northwest Suburbs?
Pure Comfort Heating and Cooling is a Lennox Premier Dealer in Streamwood, IL. Diagnostics are $75, or $99 on evenings, weekends and holidays, and you approve a flat-rate price before any repair. Phones are answered 24/7.
Frequently Asked Questions
Will my Lennox furnace reset itself after code 270?
Code 270 is a soft lockout, so the control will typically retry after the lockout period. If the underlying problem is still there, it will lock out again.
Is a dirty flame sensor the most common cause?
It is one of the most common causes, along with a weak ignitor. A technician can test the flame current to tell which part is at fault.
Should I keep resetting the furnace?
One restart is fine. Repeated resets can let gas build up without lighting. If it locks out again, call for service.
What’s the difference between code 270 and code 290?
Code 270 means no flame was sensed after several tries. Code 290 means the ignitor circuit itself has failed. A bad ignitor can cause both.
We service Lennox furnaces from our shop in Streamwood across Streamwood, Bartlett, Hoffman Estates, Schaumburg, Elgin, Hanover Park, Roselle and the rest of the Northwest Suburbs.
Looking up a different code? See our full Lennox furnace error code guide.