❄️Air Conditioner

3 FLASHES 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 3 FLASHES YELLOW Error Fix: Compressor Thermal Overload

The compressor internal thermal overload protector has tripped. Compressor motor has overheated. Causes: low refrigerant, dirty condenser coil, restricted airflow, compressor wear, or high ambient temperature. Must cool down before overload resets (30–60 minutes).

High severity2 fixes available✨ Free fix available

Quick Answer

Error 3 FLASHES YELLOW on the Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner means: Compressor Thermal Overload. The top-ranked community fix is “Test Compressor and Replace if Faulty” (hard difficulty, ~120 min, DIY cost: $0). 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:

This is a high severity error — continued use may cause damage or a safety hazard
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: $400-$600.

Other Lennox Models with Error 3 FLASHES YELLOW

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

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

ALERT 2

Communication Loss — Indoor Unit

2 fixes

People Also Ask About Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner Error 3 FLASHES YELLOW

What does error code 3 FLASHES YELLOW mean on a Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner?

Error code 3 FLASHES YELLOW on the Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner means: Compressor Thermal Overload. The compressor internal thermal overload protector has tripped. Compressor motor has overheated. Causes: low refrigerant, dirty condenser coil, restricted airflow, compressor wear, or high ambient temperature. Must cool down before overload resets (30–60 minutes).

How do I fix error code 3 FLASHES YELLOW on my Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner?

The most successful fix is "Test Compressor and Replace if Faulty" (hard difficulty, ~120 minutes). This fix costs nothing. HomeMD has 2 community-ranked fixes for this error.

Is error code 3 FLASHES YELLOW on a Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner serious?

This error is rated high severity. You should address it promptly — continued use could cause damage or safety concerns.

Can I fix Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner error 3 FLASHES YELLOW myself?

Yes — the top-ranked community fix ("Test Compressor and Replace if Faulty") is rated hard difficulty and takes about 120 minutes. Tools needed: T20 Torx screwdriver, Multimeter, Refrigerant recovery machine, Manifold gauge set, Vacuum pump, Wrenches.

How much does it cost to repair Lennox XC21 Dave Lennox Signature Collection 21 SEER Variable-Capacity Air Conditioner error 3 FLASHES YELLOW?

DIY cost: $0. Professional repair typically costs $400-$600. 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), 4 FLASHES YELLOW (Short-Cycle Protection), ALERT 1 (Communication Loss — Outdoor Unit), ALERT 11 (High Pressure Protection — Outdoor Unit), and 3 more.

Which other Lennox models have the 3 FLASHES YELLOW error?

Error code 3 FLASHES YELLOW also appears on 4 other Lennox models: 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)
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)
ALERT 2 — Communication Loss — Indoor Unit (2 fixes)

Which other Lennox models have the 3 FLASHES YELLOW error?

Error code 3 FLASHES YELLOW also appears on 4 other Lennox models:

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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