What It Means
- Error on room temperature sensor of indoor unit (Short or Open)
Lennox Split & Multi-Split
Lennox Split & Multi-Split Error Code E121
Split & Multi-Split: Mini-split unit (outdoor)
Causes & actions from Lennox
How it shows
- mini outdoor inverter pcb: E121
- Mini-split outdoor main board: E121
Indoor unit Room Thermistor Open/Short
Applicable models & manual sources
- 3WPD036S6S-1P
Error on room temperature sensor of indoor unit (Short or Open)
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.
