What It Means
- No voltage to M4 board or defective board
Lennox Unit controller
Lennox Unit controller Error Code Steady Off
Unit controller
Causes & actions from Lennox
How it shows
- m4 heartbeat D33: Steady Off
This manual entry does not list further causes or actions.
Applicable models & manual sources
- MODEL L - M4 UNIT CONTROLLER
No voltage to M4 board or defective board
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.
