HVACopediaLennox · Furnace
LED1 SLOW flash / LED2 OFF Flame sensed with gas valve not energized
What the control is telling you
The control sees flame when the gas valve should be closed. Code listed only in Table 4; the chart gives no causes or steps for it.
Applies to: G43UF-24B-045 through G43UF-60D-135 (SureLight boards 32M88, 78M47, 100973-01)
Test and repair steps
- Gas work qualified gas tech only.
- Shut off the gas at the manual valve if flame stays after the heat call ends and have the gas valve checked.
Settings for these units
- Recommended filter size by cabinet width · EL296UHV
- Recommended filter size by cabinet width · Lennox SL280UHV
- Filter sizes by cabinet width · Lennox ML180UHE
- Filter sizes (filter rack kits) · Lennox EL195UHNE
- Filter sizes by cabinet width · Lennox SL297NV
Models that show this code
10 models in Lennox G43UF
Other codes on the same units
- LED1 OFF / LED2 OFF No power to the control
- LED1 OFF / LED2 ON Control board failure or control wired incorrectly
- LED1 OFF / LED2 SLOW flash Prove switch (pressure switch) open
- LED1 ON / LED2 OFF Control board failure or control wired incorrectly
- LED1 ON / LED2 ON Control board failure or control wired incorrectly
- LED1 ON / LED2 SLOW flash Rollout switch open
- LED1 SLOW flash / LED2 FAST flash Low flame signal
- LED1 SLOW flash / LED2 ON Primary or secondary limit open
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Source: Lennox G43UF Unit Information Corp. 0416-L4 (rev 2-2006), Table 4 Diagnostic Codes p.11. Summarized in our own words; check the original manual for your model.
Homeowner looking at this code? See what it means for you and when to call a technician.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.