What It Means
- DIRTY AIR FILTER
Lennox Unit controller
Lennox Unit controller Error Code 6
Unit controller
Causes & actions from Lennox
How it shows
- M4 alarm code: 6
Dirty filter switch is detected as closed and will automatically clear once switch is detected open. Replace filter or check filter switch S27.
Applicable models & manual sources
- MODEL L - M4 UNIT CONTROLLER
DIRTY AIR FILTER
MODEL L - M4 UNIT CONTROLLER, M4 Unit Controller
Disclaimer: This information is for general reference. Code wording and instructions vary by model. Always follow the service manual for your exact unit.
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