What It Means
- HEAT 1 CAI SWITCH S18
Lennox Unit controller
Lennox Error Code 56
Unit controller
Causes & actions from Lennox
How it shows
- M4 alarm code: 56
Check heat section 1 combustion air motor and proof switch.
Applicable models & manual sources
- MODEL L - M4 UNIT CONTROLLER
HEAT 1 CAI SWITCH S18
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.
What should you check next?
Continue in ACLogics with guided diagnosis for your equipment and symptoms.
