Lennox XP21 Dave Lennox Signature Collection 20 SEER Heat Pump NO LIGHT Error Fix: No Power to Outdoor Unit

Error code NO LIGHT on the Lennox XP21 Dave Lennox Signature Collection 20 SEER Heat Pump means: No Power to Outdoor Unit. The control board has no power. Check the outdoor disconnect switch, circuit breaker, and fuse (if equipped) in the disconnect box.

The most successful fix is "Test and Replace Outdoor Unit Control Board" (hard difficulty, ~120 minutes). Estimated DIY cost: $0-$20. HomeMD has 2 community-ranked fixes for this error.

This error is rated critical severity. It is generally not urgent and can often be resolved with a simple DIY fix.

Yes — the top-ranked community fix ("Test and Replace Outdoor Unit Control Board") is rated hard difficulty and takes about 120 minutes. Tools needed: T15 Torx screwdriver, Multimeter, Needle nose pliers.

DIY cost: $0-$20. Professional repair typically costs $400-$700. Many homeowners save money by trying the top-ranked community fix first.

The Lennox XP21 Dave Lennox Signature Collection 20 SEER Heat Pump has 8 other known error codes, including: 1 FLASH YELLOW (High Pressure Switch Open), 2 FLASHES YELLOW (Low Pressure Switch Open), 3 FLASHES YELLOW (Compressor Thermal Overload), 4 FLASHES YELLOW (Short-Cycle Protection), ALERT 1 (Communication Loss — Outdoor Unit), and 3 more.

Error code NO LIGHT also appears on 9 other Lennox models: CBX27UH Lennox Variable Speed Air Handler, EL296V Elite Series 96% AFUE Two-Stage Variable Speed Gas Furnace, ML14XC1 Merit Series 14 SEER Single-Stage Air Conditioner, ML196E Merit Series 96% AFUE Single-Stage Gas Furnace, SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace, SL297NV Dave Lennox Signature Collection 97% AFUE Modulating Variable Speed Gas Furnace, and 3 more. The fix may vary by model, so check each model's specific page for tailored repair steps.