What It Means
- SECONDARY HEAT 1 LIMIT OPEN S21
Lennox Unit controller
Lennox Error Code 52
Unit controller
Causes & actions from Lennox
How it shows
- M4 alarm code: 52
Heat section 1 secondary gas heat limit switch is open. Check air flow, air filter, limit switch and wiring.
Applicable models & manual sources
- MODEL L - M4 UNIT CONTROLLER
SECONDARY HEAT 1 LIMIT OPEN S21
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.
