OEM Control Family: Lennox SureLight (56L84 / 97L48 / 83M00 / 103085-03) • Ducane • Aire-Flo
Lennox Furnace Dual Red & Green LED Decoder: SureLight DS1 + DS2 Matrix
⚡ Instant OEM Answer (Lennox Dual Red DS1 + Green DS2 LEDs):
Lennox SureLight boards pair a Red (DS1) and Green (DS2) LED: Simultaneous Slow Flash means normal standby; Alternating Slow Flash means 60-minute Watchguard Ignition Lockout (clean
52W29 flame sensor below 1.5 µA DC or check 11–19 Ω Nitride igniter); Red OFF + Green Slow Flash means Pressure Switch open; and Red Slow Flash + Green OFF means Primary High Limit open.
Dual-LED DS1 & DS2 Reference
Complete Lennox SureLight DS1 (Red) + DS2 (Green) Combination Table
Applies to Lennox G40UH, G43UF, G50UH, G51MP, G60UH, G61MPV, ML180, ML193, EL195, Ducane 80G1/92G1, and Aire-Flo furnaces equipped with dual-LED SureLight integrated controls (56L84, 63K89, 83M00, 97L48, 103085-03).
| Red LED (DS1) | Green LED (DS2) | Lennox OEM Fault Meaning | Replacement Part SKU & Triage Fix |
|---|---|---|---|
| Slow Flash (Together) | Slow Flash (Together) | Normal Standby — Power OK | Zero faults. Simultaneous Fast Flash = Active Heating Demand. |
| Alternating Slow | Alternating Slow | 60-Min Watchguard Ignition Lockout | Polish 52W29 / 69W43 Flame Sensor ($0) or swap 768A-845 / 41K56 Igniter ($45). |
| OFF | Slow Flash | Pressure Switch Open / Blocked Flue | Flush Lennox condensate trap, clear PVC vent snow, or test 80W52 / 11U64 Switch. |
| OFF | Fast Flash | Pressure Switch Closed Before Inducer | Drain condensate water droplet from silicone hose or replace welded pressure switch. |
| Slow Flash | OFF | Primary High Limit Switch Open | Replace dirty air filter immediately; check closed vents & blower run capacitor µF. |
| Fast Flash | OFF | Manual Flame Rollout Switch Open | CRITICAL: Inspect heat exchanger & burner vestibule before pressing rollout reset button. |
| Alternating Fast | Alternating Fast | Improper 120V Line Polarity / Ground | Verify 120 VAC L1-to-Ground and < 2.0 VAC Neutral-to-Ground (or add generator bonding plug). |
| Steady ON | Steady ON (Or Both OFF) | Internal Control Fault or Open 3A Fuse | Check 3A purple blade fuse & 24VAC transformer; if solid ON with 24VAC present, replace board. |