E240 Low flame current (run mode)

What the control is telling you

Flame signal is weak while running.

Applies to: EL296UHV(X) series furnaces (integrated control 103130-XX and 107045-XX)

Likely causes

• Dirty or oxidized flame sensor
• Poor unit ground
• Burner/flame not contacting sensor

Test and repair steps

1. Enter Flame Signal mode hold the diagnostic push button until a solid F shows, release, and read flame current in microamps.
2. Compare 2.6 uA or more is normal, 2.5 uA or less is low, and the flame drops out at 1.1 uA.
3. Warning: Turn off power and gas before removing the flame sensor from the left side of the burner support.
4. Clean the sensor rod (remove oxide) or replace it if damaged or still weak after cleaning.
5. Measure neutral-to-ground voltage and verify the furnace has a solid earth ground; the control is polarity sensitive.
6. Check ground at the control AC volts between line neutral and the C terminal should not exceed 2 VAC at idle, 5 VAC with inducer/ignitor on, 10 VAC with blower on; a wide swing under load means a poor ground. Line hot to neutral should be 97-132 VAC.
7. Check gas pressures with a manometer supply natural gas 4.5-13.0 in. w.c. (LP 11.0-13.0); manifold natural 1.7 low fire / 3.5 high fire (LP 4.5 / 10.0) at 0-4500 ft.
8. Clean burners if dirty (soft brush vacuum on burner faces) and confirm burners are centered in the burner ports.
9. Run a heat cycle and confirm stable flame current.

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 by cabinet width · Lennox SL297NV