❄️Air Conditioner

ALERT 12

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

Lennox XC25 Dave Lennox Signature Collection 26 SEER Variable-Capacity Air Conditioner ALERT 12 Error Fix: Low Pressure Protection — Outdoor Unit

The low-pressure safety switch has tripped. Causes: low refrigerant charge (leak), frozen indoor evaporator coil, restricted metering device, kinked liquid line, or low outdoor temperature operation. Low refrigerant charge is most common and requires leak repair by a licensed technician.

High severity2 fixes available✨ Free fix available

Quick Answer

Error ALERT 12 on the Lennox XC25 Dave Lennox Signature Collection 26 SEER Variable-Capacity Air Conditioner means: Low Pressure Protection — Outdoor Unit. The top-ranked community fix is “Test and Repair Refrigerant Leak and Replace Metering Device” (hard difficulty, ~120 min, DIY cost: $0-$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:

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-$650.

Other Lennox Models with Error ALERT 12

XC21 Dave Lennox Signature Collection 21 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 XC25 Dave Lennox Signature Collection 26 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 14

Compressor Discharge Temperature High

2 fixes

ALERT 2

Communication Loss — Indoor Unit

2 fixes

People Also Ask About Lennox XC25 Dave Lennox Signature Collection 26 SEER Variable-Capacity Air Conditioner Error ALERT 12

What does error code ALERT 12 mean on a Lennox XC25 Dave Lennox Signature Collection 26 SEER Variable-Capacity Air Conditioner?

Error code ALERT 12 on the Lennox XC25 Dave Lennox Signature Collection 26 SEER Variable-Capacity Air Conditioner means: Low Pressure Protection — Outdoor Unit. The low-pressure safety switch has tripped. Causes: low refrigerant charge (leak), frozen indoor evaporator coil, restricted metering device, kinked liquid line, or low outdoor temperature operation. Low refrigerant charge is most common and requires leak repair by a licensed technician.

How do I fix error code ALERT 12 on my Lennox XC25 Dave Lennox Signature Collection 26 SEER Variable-Capacity Air Conditioner?

The most successful fix is "Test and Repair Refrigerant Leak and Replace Metering Device" (hard difficulty, ~120 minutes). Estimated DIY cost: $0-$20. HomeMD has 2 community-ranked fixes for this error.

Is error code ALERT 12 on a Lennox XC25 Dave Lennox Signature Collection 26 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 XC25 Dave Lennox Signature Collection 26 SEER Variable-Capacity Air Conditioner error ALERT 12 myself?

Yes — the top-ranked community fix ("Test and Repair Refrigerant Leak and Replace Metering Device") is rated hard difficulty and takes about 120 minutes. Tools needed: Electronic leak detector, Vacuum pump, Manifold gauge set, Refrigerant scale, Adjustable wrench, Safety goggles, Gloves.

How much does it cost to repair Lennox XC25 Dave Lennox Signature Collection 26 SEER Variable-Capacity Air Conditioner error ALERT 12?

DIY cost: $0-$20. Professional repair typically costs $400-$650. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the Lennox XC25 Dave Lennox Signature Collection 26 SEER Variable-Capacity Air Conditioner have?

The Lennox XC25 Dave Lennox Signature Collection 26 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 ALERT 12 error?

Error code ALERT 12 also appears on 3 other Lennox models: XC21 Dave Lennox Signature Collection 21 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 XC25 Dave Lennox Signature Collection 26 SEER Variable-Capacity Air Conditioner have?

The Lennox XC25 Dave Lennox Signature Collection 26 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 14 — Compressor Discharge Temperature High (2 fixes)
ALERT 2 — Communication Loss — Indoor Unit (2 fixes)

Which other Lennox models have the ALERT 12 error?

Error code ALERT 12 also appears on 3 other Lennox models:

XC21 Dave Lennox Signature Collection 21 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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