What It Means
- SMOKE DETECTED
Lennox Unit controller
Lennox Unit controller Error Code 4
Unit controller
Causes & actions from Lennox
How it shows
- M4 alarm code: 4
A173 input is sensed as closed. Will automatically clears once input is detected open. For smoke mode, check for source of smoke. While Smoke Alarm is active, the CORE Unit Controller will not service any cooling, heating or ventilation demands.
Applicable models & manual sources
- MODEL L - M4 UNIT CONTROLLER
SMOKE DETECTED
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.
