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4 FLASHES

Lennox · SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace

Lennox SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace 4 FLASHES Error Fix: Pressure Switch Open — Did Not Close

The draft inducer motor is running but the pressure switch did not close within the expected time. This is one of the most common Lennox furnace fault codes. Causes: blocked exhaust vent (ice, bird nest, debris), clogged condensate drain (high-efficiency 90%+ units), cracked or kinked pressure switch hose, weak or failing draft inducer motor, or a bad pressure switch. Check the exhaust vent termination outside the home first — #1 cause in winter.

High severity2 fixes available

Quick Answer

Error 4 FLASHES on the Lennox SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace means: Pressure Switch Open — Did Not Close. The top-ranked community fix is “Test and Replace Pressure Switch or Draft Inducer Motor” (hard difficulty, ~75 min, DIY cost: $30-$50). 2 community-ranked fixes available below.

Published February 2026 · 2 fixes · furnace

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 furnace 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: $150-$220.

Other Lennox Models with Error 4 FLASHES

EL296V Elite Series 96% AFUE Two-Stage Variable Speed Gas Furnace

furnace · 2 fixes

ML196E Merit Series 96% AFUE Single-Stage Gas Furnace

furnace · 2 fixes

SL297NV Dave Lennox Signature Collection 97% AFUE Modulating Variable Speed Gas Furnace

furnace · 2 fixes

Other Lennox SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace Error Codes

1 FLASH

No Previous Fault Code Stored

2 fixes

10 FLASHES

Blower Motor Calibration Fault

2 fixes

11 FLASHES

Auxiliary Limit Switch Open

Inducer Motor Fault

Communicating System Fault

2 fixes

2 FLASHES

System Lockout — Retries Exhausted

2 fixes

3 FLASHES

Pressure Switch Stuck Closed

2 fixes

5 FLASHES

Flame Sensed Without Call for Heat

2 fixes

People Also Ask About Lennox SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace Error 4 FLASHES

What does error code 4 FLASHES mean on a Lennox SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace?

Error code 4 FLASHES on the Lennox SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace means: Pressure Switch Open — Did Not Close. The draft inducer motor is running but the pressure switch did not close within the expected time. This is one of the most common Lennox furnace fault codes. Causes: blocked exhaust vent (ice, bird nest, debris), clogged condensate drain (high-efficiency 90%+ units), cracked or kinked pressure switch hose, weak or failing draft inducer motor, or a bad pressure switch. Check the exhaust vent termination outside the home first — #1 cause in winter.

How do I fix error code 4 FLASHES on my Lennox SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace?

The most successful fix is "Test and Replace Pressure Switch or Draft Inducer Motor" (hard difficulty, ~75 minutes). Estimated DIY cost: $30-$50. HomeMD has 2 community-ranked fixes for this error.

Is error code 4 FLASHES on a Lennox SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace serious?

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

Can I fix Lennox SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace error 4 FLASHES myself?

Yes — the top-ranked community fix ("Test and Replace Pressure Switch or Draft Inducer Motor") is rated hard difficulty and takes about 75 minutes. Tools needed: T20 Torx screwdriver, Multimeter, Nut driver set.

How much does it cost to repair Lennox SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace error 4 FLASHES?

DIY cost: $30-$50. Professional repair typically costs $150-$220. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the Lennox SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace have?

The Lennox SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace has 8 other known error codes, including: 1 FLASH (No Previous Fault Code Stored), 10 FLASHES (Blower Motor Calibration Fault), 11 FLASHES (Auxiliary Limit Switch Open), 12 FLASHES (Inducer Motor Fault), 13 FLASHES (Communicating System Fault), and 3 more.

Which other Lennox models have the 4 FLASHES error?

Error code 4 FLASHES also appears on 3 other Lennox models: EL296V Elite Series 96% AFUE Two-Stage Variable Speed Gas Furnace, ML196E Merit Series 96% AFUE Single-Stage Gas Furnace, SL297NV Dave Lennox Signature Collection 97% AFUE Modulating Variable Speed Gas Furnace. The fix may vary by model, so check each model's specific page for tailored repair steps.

What other error codes does the Lennox SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace have?

The Lennox SL280V Dave Lennox Signature Collection 80% AFUE Variable Speed Gas Furnace has 8 other known error codes:

1 FLASH — No Previous Fault Code Stored (2 fixes)
10 FLASHES — Blower Motor Calibration Fault (2 fixes)
11 FLASHES — Auxiliary Limit Switch Open (2 fixes)
12 FLASHES — Inducer Motor Fault (2 fixes)
13 FLASHES — Communicating System Fault (2 fixes)
2 FLASHES — System Lockout — Retries Exhausted (2 fixes)
3 FLASHES — Pressure Switch Stuck Closed (2 fixes)
5 FLASHES — Flame Sensed Without Call for Heat (2 fixes)

Which other Lennox models have the 4 FLASHES error?

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

EL296V Elite Series 96% AFUE Two-Stage Variable Speed Gas Furnace (furnace) · 2 fixes
ML196E Merit Series 96% AFUE Single-Stage Gas Furnace (furnace) · 2 fixes
SL297NV Dave Lennox Signature Collection 97% AFUE Modulating Variable Speed Gas Furnace (furnace) · 2 fixes

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