HVACopediaLennox · Furnace
4 flashes Low flame signal
What the control is telling you
Flame signal is weak. The control keeps running but warns that the flame sensor needs attention.
Applies to: EL195UHNE furnaces with ignition control 103217-03 or 107163-01 (red LED)
Likely causes
- Oxidized or dirty flame sensor
- Sensor bent away from flame
- Poor ground
- Incorrect combustion (manifold/air orifice)
Test and repair steps
- Use the recall button / meter to read flame current. Read flame signal: normal 2.6 uA or more, low 2.5 uA or less, drop-out 1.1 uA (Table 7). Note: the troubleshooting flowchart uses 1.5 uA as the low limit.
- Warning: Shut off power and gas before removing the sensor (top of the air gas plenum).
- Clean the sensor rod and check its position; replace if damaged.
- Check the burner ground and Check ground at the control: AC volts between line neutral and the C terminal should be about 0.3 V (2 V max) at idle, 0.75 V (5 V max) with inducer/ignitor on, under 2 V (10 V max) with blower on; line hot to neutral should be 97-132 VAC.
- Check manifold pressure and the air orifice size if the flame is poor.
Settings for these units
- Filter sizes (filter rack kits) · Lennox EL195UHNE
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Source: Lennox EL195UHNE Unit Information Corp 1801-L1 (rev 04/2024), Table 4 (103217-03) / Table 5 (107163-01) diagnostic codes, p.8-10; Table 7, p.12. Summarized in our own words; check the original manual for your model.
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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.