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Lennox 6 Flashes — Pressure Switch System Lockout

6 flashes

Persistent pressure switch errors caused lockout.

Brand: Lennox (Also covers Armstrong Air, Aire-Flo, Ducane)  |  Equipment: Gas Furnace

What This Code Means

6 flashes means the control has seen repeated pressure switch errors and entered lockout. Same root causes as code 3 but escalated.

Likely Causes (Ranked)

Common

Persistent vent blockage

What: Ongoing exhaust obstruction.

How to check: Inspect exhaust outlet.

Fix: Clear blockage.

Shop parts
Common

Failed inducer

What: Inducer not creating consistent draft.

How to check: Listen and feel for draft.

Fix: Replace inducer.

Shop parts
Common

Bad pressure switch

What: Switch fails intermittently.

How to check: Tech test.

Fix: Replace.

Shop parts

Diagnostic Steps

  1. Cut power 60s to clear lockout
  2. Inspect exhaust
  3. Check inducer
  4. Replace switch if needed

Frequently Asked Questions

Difference between Lennox 3 and 6 flashes?
Both are pressure switch issues; 6 means it's locked out after repeated 3 errors.
DIY fix?
Vent clearing yes. Component replacement varies.
Same on Armstrong?
Yes.

Related Lennox Codes

Lennox Error Code 3 FlashesLennox Error Code 2 Flashes

Related Symptoms

Furnace Not Igniting

Need More Help?

Try our interactive symptom diagnostic tool or browse Lennox parts.

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