What It Means
- Error on indoor temperature sensor (Short or Open)
Lennox Air handler
Lennox Air handler Error Code E121
Air handler: Air handler (indoor)
Causes & actions from Lennox
How it shows
- mmd m6 receiver concealed led: green off, red off, led3 flashing, led4 off, led5 off (green: off, led3: flashing, led4: off, led5: off, red: off)
- mmd m6 receiver standard led: led1 off, led2 off, led3 flashing, led4 off, led5 off (led1: off, led2: off, led3: flashing, led4: off, led5: off)
- samsung receiver concealed led: GREEN off, RED off, Timer icon blinking, Fan icon off, Filter icon off
- samsung receiver error label: E121
- samsung receiver standard led: Power icon off, Snowflake/drop icon off, Timer icon blinking, Fan icon off, Filter icon off
This manual entry does not list further causes or actions.
Applicable models & manual sources
- MMD***M6-1P
Error on indoor temperature sensor (Short or Open)
- MMD***S6-1P
Error on indoor temperature sensor (Short or Open)
- MMD***S6-1P
Error on indoor temperature sensor (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.
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