Lennox Error Code 12 flashes: Flame sensed with gas valve off (Furnace)
Lennox error code 12 flashes on a furnace means: Flame sensed with gas valve off. It is also called Lennox diagnostic code 12 flashes.
Homeowner? What Lennox code 12 flashes means for you
Stop and call Your furnace is reporting: Flame sensed with gas valve off. This code is a safety shutdown. Turn the furnace off and call a licensed technician. Do not keep resetting it. If you smell gas, leave the house and call your gas utility or 911 from outside.
Safe things you can check yourself
- Check the thermostat: right mode (Heat or Cool), set a few degrees past room temperature, and fresh batteries if it uses them.
- Make sure the unit has power: its on/off switch (often looks like a light switch near the unit) is ON and the breaker in the electrical panel is not tripped.
Call (647) 657-2977Book a service call
Licensed technicians serving Vaughan, Toronto and the GTA.
What does Lennox error code 12 flashes mean?
The control senses flame when the gas valve should be closed. Gas valve stays off, inducer on, blower on heating speed.
Applies to: EL195UHNE furnaces with ignition control 103217-03 or 107163-01 (red LED)
Common causes of Lennox code 12 flashes
- Gas valve leaking through
- Gas valve energized by miswiring
- Flame sensor shorted to ground / control fault
Lennox models that use code 12 flashes
EL195UH040NE36BEL195UH060NE36BEL195UH080NE48CEL195UH100NE60C
Other Lennox Furnace codes
All Lennox Furnace error codes →
Lennox code 12 flashes: homeowner questions
What does Lennox code 12 flashes mean?
Flame sensed with gas valve off. The control senses flame when the gas valve should be closed. Gas valve stays off, inducer on, blower on heating speed.
Is it safe to keep using my furnace with code 12 flashes?
No. Code 12 flashes is a safety shutdown, so keep the furnace off until a licensed technician has checked it.
Can I reset Lennox code 12 flashes myself?
Do not keep resetting it. Repeated resets can hide a safety problem; a licensed technician needs to find the cause.
Who can fix Lennox code 12 flashes near me?
Aurora Star Tech Inc. repairs Lennox furnaces in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.
Homeowner help: Furnace Not Turning On: What to Check · Furnace Blinking Light: What the Flash Codes Mean
Troubleshooting guides
- Blowing cold air All brands · Furnace
- No heat All brands · Furnace
- Short cycling All brands · Furnace
- Blower motor does not run - Lennox SL280UHV ECM checks Lennox · Furnace
- Display shows two horizontal bars (soft disable) - Lennox SL297NV Lennox · Furnace
- Furnace will not run (no heat) - Lennox EL195UHNE Lennox · Furnace
- Furnace will not run (no heat) - Lennox SL297NV Lennox · Furnace
- Furnace will not run - Lennox SL280UHV checklist Lennox · Furnace
- Indoor blower does not run - Lennox EL195UHNE Lennox · Furnace
- Indoor blower does not run - Lennox ML180UHE Lennox · Furnace
- Poor ignition or combustion resonance - Lennox EL195UHNE Lennox · Furnace
- Poor ignition or loud combustion resonance - Lennox SL280UHNV Lennox · Furnace
- Two horizontal lines on display (soft disable) - Lennox communicating Lennox · Furnace
Source: Lennox EL195UHNE Unit Information Corp 1801-L1 (rev 04/2024), Table 4 (103217-03) / Table 5 (107163-01) diagnostic codes, p.8-10; flowchart p.51. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.