❄️Air Conditioner

SOLID YELLOW

Lennox · XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner

Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner SOLID YELLOW Error Fix: Low Voltage Warning

Outdoor unit control board detecting low incoming voltage (below minimum operating voltage, typically 197 VAC for 208/230V units). Causes: utility voltage sag, undersized wire gauge, loose connections, failing contactor contacts. Measure voltage at unit disconnect — should be 208–253 VAC.

Medium severity2 fixes available✨ Free fix available

Quick Answer

Error SOLID YELLOW on the Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner means: Low Voltage Warning. The top-ranked community fix is “Diagnose and Repair Low Voltage Issues Including Wire Gauge and Contactor” (medium difficulty, ~90 min, DIY cost: $10-$20). 2 community-ranked fixes available below.

Published February 2026 · 2 fixes · air conditioner

Content is based on manufacturer service documentation, community repair experience, and OEM technical bulletins. Always verify with your owner's manual.Learn about our editorial standards.

When to Call a Professional

While many air conditioner repairs can be done safely at home, consider hiring a qualified technician if:

The repair involves electrical wiring, gas lines, or refrigerant
You've tried the top-ranked fix and the error persists
You smell gas, see sparking, or notice water leaking
The repair requires specialized tools you don't have
Your appliance is still under manufacturer warranty

Average professional repair cost for this issue: $250-$450.

Other Lennox Models with Error SOLID YELLOW

CBX27UH Lennox Variable Speed Air Handler

air_handler · 2 fixes

ML14XC1 Merit Series 14 SEER Single-Stage Air Conditioner

air_conditioner · 2 fixes

XC25 Dave Lennox Signature Collection 26 SEER Variable-Capacity Air Conditioner

air_conditioner · 2 fixes

XP21 Dave Lennox Signature Collection 20 SEER Heat Pump

heat_pump · 2 fixes

XP25 Dave Lennox Signature Collection Variable-Capacity Heat Pump

heat_pump · 2 fixes

Other Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner Error Codes

1 FLASH YELLOW

High Pressure Switch Open

2 fixes

2 FLASHES YELLOW

Low Pressure Switch Open

2 fixes

3 FLASHES YELLOW

Compressor Thermal Overload

2 fixes

4 FLASHES YELLOW

Short-Cycle Protection

2 fixes

ALERT 1

Communication Loss — Outdoor Unit

2 fixes

ALERT 11

High Pressure Protection — Outdoor Unit

2 fixes

ALERT 12

Low Pressure Protection — Outdoor Unit

2 fixes

ALERT 14

Compressor Discharge Temperature High

2 fixes

People Also Ask About Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner Error SOLID YELLOW

What does error code SOLID YELLOW mean on a Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner?

Error code SOLID YELLOW on the Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner means: Low Voltage Warning. Outdoor unit control board detecting low incoming voltage (below minimum operating voltage, typically 197 VAC for 208/230V units). Causes: utility voltage sag, undersized wire gauge, loose connections, failing contactor contacts. Measure voltage at unit disconnect — should be 208–253 VAC.

How do I fix error code SOLID YELLOW on my Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner?

The most successful fix is "Diagnose and Repair Low Voltage Issues Including Wire Gauge and Contactor" (medium difficulty, ~90 minutes). Estimated DIY cost: $10-$20. HomeMD has 2 community-ranked fixes for this error.

Is error code SOLID YELLOW on a Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner serious?

This error is rated medium severity. It should be addressed soon, but your appliance may still function in a limited capacity.

Can I fix Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner error SOLID YELLOW myself?

Yes — the top-ranked community fix ("Diagnose and Repair Low Voltage Issues Including Wire Gauge and Contactor") is rated medium difficulty and takes about 90 minutes. Tools needed: T20 Torx screwdriver, Multimeter, Nut driver set, Wire gauge tool.

How much does it cost to repair Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner error SOLID YELLOW?

DIY cost: $10-$20. Professional repair typically costs $250-$450. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner have?

The Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner 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.

Which other Lennox models have the SOLID YELLOW error?

Error code SOLID YELLOW also appears on 5 other Lennox models: CBX27UH Lennox Variable Speed Air Handler, ML14XC1 Merit Series 14 SEER Single-Stage Air Conditioner, XC25 Dave Lennox Signature Collection 26 SEER Variable-Capacity Air Conditioner, XP21 Dave Lennox Signature Collection 20 SEER Heat Pump, XP25 Dave Lennox Signature Collection Variable-Capacity Heat Pump. The fix may vary by model, so check each model's specific page for tailored repair steps.

What other error codes does the Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner have?

The Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner has 8 other known error codes:

1 FLASH YELLOW — High Pressure Switch Open (2 fixes)
2 FLASHES YELLOW — Low Pressure Switch Open (2 fixes)
3 FLASHES YELLOW — Compressor Thermal Overload (2 fixes)
4 FLASHES YELLOW — Short-Cycle Protection (2 fixes)
ALERT 1 — Communication Loss — Outdoor Unit (2 fixes)
ALERT 11 — High Pressure Protection — Outdoor Unit (2 fixes)
ALERT 12 — Low Pressure Protection — Outdoor Unit (2 fixes)
ALERT 14 — Compressor Discharge Temperature High (2 fixes)

Which other Lennox models have the SOLID YELLOW error?

Error code SOLID YELLOW also appears on 5 other Lennox models:

CBX27UH Lennox Variable Speed Air Handler (air handler) · 2 fixes
ML14XC1 Merit Series 14 SEER Single-Stage Air Conditioner (air conditioner) · 2 fixes
XC25 Dave Lennox Signature Collection 26 SEER Variable-Capacity Air Conditioner (air conditioner) · 2 fixes
XP21 Dave Lennox Signature Collection 20 SEER Heat Pump (heat pump) · 2 fixes
XP25 Dave Lennox Signature Collection Variable-Capacity Heat Pump (heat pump) · 2 fixes

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