Lennox
Lennox Air Conditioners Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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E200
Lennox air conditioner will not start; thermostat calling for cooling but outdoor unit is completely dead, no fan, no compressor, no click from contactor.
Low Voltage Control Circuit Fault
E201
Lennox air conditioner outdoor unit runs briefly then shuts down; control board or thermostat shows E201 low-voltage error.
Intermittent Low Voltage Supply
E202
Lennox air conditioner does not respond to thermostat; control board indicates E202 communication fault between indoor and outdoor units (common on communicating Lennox systems with iComfort thermostats).
Communication Bus Failure
E223
Lennox communicating air conditioner shows E223 or similar high-pressure/overload error; outdoor unit starts then quickly shuts off, often on very hot days.
High Refrigerant Pressure Trip
E227
Lennox air conditioner displays E227 or similar low-pressure/low-suction error; outdoor unit may short-cycle or run with poor cooling performance.
Low Refrigerant Pressure Trip
E250
Lennox communicating thermostat reports E250 outdoor unit lockout; system will not cool until power is cycled or lockout is cleared.
Compressor Protection Lockout
E312
Lennox iComfort thermostat shows E312 indoor blower fault when cooling is requested; outdoor unit may run but little or no air comes from vents.
Indoor Blower Motor Failure
E351
Lennox thermostat shows E351 outdoor temperature sensor error; system may still cool but displays incorrect outdoor temperature or uses wrong staging.
Outdoor Temperature Sensor Fault
E353
Lennox communicating system shows E353 discharge air temperature sensor error; system may shut down or run erratically.
Discharge Air Temperature Sensor Fault
E411
Lennox thermostat or control shows E411 high temperature limit or coil temperature fault during cooling; system shuts down to protect components.
Evaporator Coil Overtemperature / Airflow Fault
E413
Lennox system displays E413 evaporator freeze protection or low coil temperature fault; coil may be iced over and airflow is weak.
Evaporator Coil Freeze-Up
E420
Lennox communicating thermostat shows E420 high line voltage or power quality error; system may lock out or run intermittently.
High Line Voltage / Power Quality Fault
E422
Lennox system reports E422 low line voltage; outdoor unit may not start or may drop out during compressor start.
Low Line Voltage / Brownout Condition
E430
Lennox thermostat shows E430 indoor humidity sensor error; dehumidification features may not work correctly during cooling.
Indoor Humidity Sensor Fault
E440
Lennox communicating system shows E440 indoor unit configuration or model mismatch error; system may not operate or may run in backup mode.
Configuration / Model Mismatch Fault
E441
Lennox thermostat shows E441 outdoor unit configuration error; outdoor unit may not respond correctly to staging commands.
Outdoor Unit Configuration Fault
E450
Lennox system shows E450 condensate overflow or float switch error; cooling is disabled even though thermostat is calling.
Condensate Overflow Protection Trip
E460
Lennox thermostat shows E460 indoor coil sensor out of range; system may shut down or run with limited capacity.
Indoor Coil Temperature Sensor Fault
E470
Lennox system reports E470 compressor overload or thermal protection trip; compressor shuts off and may restart after cooling down.
Compressor Overheating / Overload Trip
E480
Lennox communicating system shows E480 compressor short-cycling or minimum off-time violation; compressor starts and stops frequently.
Compressor Short Cycling Protection
Symptom
Lennox air conditioner causes lights to dim or flicker in the home when the compressor starts.
High Inrush Current / Voltage Sag
Symptom
Lennox air conditioner cycles normally but humidity in the home remains high and feels clammy.
Poor Dehumidification Performance
Symptom
Lennox air conditioner emits a burning or electrical smell when running.
Overheating Electrical Component or Dust Burn-Off
Symptom
Lennox air conditioner frequently freezes the indoor coil; ice forms on refrigerant lines and coil housing.
Evaporator Coil Freeze-Up
Symptom
Lennox air conditioner indoor blower runs but outdoor unit does not; room temperature rises and no heat is removed.
Outdoor Unit Control Circuit Open
Symptom
Lennox air conditioner makes loud buzzing or humming at the outdoor unit when trying to start, but fan and/or compressor do not run.
Failed Capacitor or Stalled Motor
Symptom
Lennox air conditioner outdoor unit runs but indoor blower does not; suction line may ice up and little or no air comes from vents.
Indoor Blower Non-Operation
Symptom
Lennox air conditioner outdoor unit runs in cold weather when it should be off (for cooling-only systems).
Stuck Contactor or Control Logic Fault
Symptom
Lennox air conditioner produces a musty or moldy smell when it starts, especially after being off for a while.
Biological Growth on Evaporator Coil or Drain Pan
Symptom
Lennox air conditioner runs but does not cool well; supply air is only slightly cooler than room temperature.
Insufficient Cooling Capacity
Symptom
Lennox air conditioner runs continuously and struggles to reach set temperature on very hot days.
Capacity or Airflow Deficiency
Symptom
Lennox air conditioner short cycles, turning on and off every few minutes without reaching set temperature.
Short Cycling Due to Control or Sizing Issues
Symptom
Lennox air conditioner thermostat display is blank or unresponsive; system does not run.
Thermostat Power Loss
Symptom
Lennox outdoor unit frequently trips the breaker when starting or during operation.
Overcurrent / Short Circuit
Symptom
Lennox outdoor unit is excessively noisy during operation, with rattling, vibrating, or metallic banging sounds.
Mechanical Vibration or Fan Imbalance
Symptom
Outdoor Lennox air conditioner unit will not turn on at all; indoor blower runs and thermostat appears normal but condenser is silent.
Outdoor Unit Power or Contactor Failure
Symptom
Outdoor Lennox condenser fan runs but compressor does not start; unit hums or is unusually quiet and no cooling is produced.
Compressor Start Failure
Symptom
Water leaking from Lennox indoor air handler or furnace cabinet during cooling; puddles form around the unit.
Condensate Drainage Failure
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| E200 |
Lennox air conditioner will not start; thermostat calling for cooling but outdoor unit is completely dead, no fan, no compressor, no click from contactor.
|
Low Voltage Control Circuit Fault | View Details |
| E201 |
Lennox air conditioner outdoor unit runs briefly then shuts down; control board or thermostat shows E201 low-voltage error.
|
Intermittent Low Voltage Supply | View Details |
| E202 |
Lennox air conditioner does not respond to thermostat; control board indicates E202 communication fault between indoor and outdoor units (common on communicating Lennox systems with iComfort thermostats).
|
Communication Bus Failure | View Details |
| E223 |
Lennox communicating air conditioner shows E223 or similar high-pressure/overload error; outdoor unit starts then quickly shuts off, often on very hot days.
|
High Refrigerant Pressure Trip | View Details |
| E227 |
Lennox air conditioner displays E227 or similar low-pressure/low-suction error; outdoor unit may short-cycle or run with poor cooling performance.
|
Low Refrigerant Pressure Trip | View Details |
| E250 |
Lennox communicating thermostat reports E250 outdoor unit lockout; system will not cool until power is cycled or lockout is cleared.
|
Compressor Protection Lockout | View Details |
| E312 |
Lennox iComfort thermostat shows E312 indoor blower fault when cooling is requested; outdoor unit may run but little or no air comes from vents.
|
Indoor Blower Motor Failure | View Details |
| E351 |
Lennox thermostat shows E351 outdoor temperature sensor error; system may still cool but displays incorrect outdoor temperature or uses wrong staging.
|
Outdoor Temperature Sensor Fault | View Details |
| E353 |
Lennox communicating system shows E353 discharge air temperature sensor error; system may shut down or run erratically.
|
Discharge Air Temperature Sensor Fault | View Details |
| E411 |
Lennox thermostat or control shows E411 high temperature limit or coil temperature fault during cooling; system shuts down to protect components.
|
Evaporator Coil Overtemperature / Airflow Fault | View Details |
| E413 |
Lennox system displays E413 evaporator freeze protection or low coil temperature fault; coil may be iced over and airflow is weak.
|
Evaporator Coil Freeze-Up | View Details |
| E420 |
Lennox communicating thermostat shows E420 high line voltage or power quality error; system may lock out or run intermittently.
|
High Line Voltage / Power Quality Fault | View Details |
| E422 |
Lennox system reports E422 low line voltage; outdoor unit may not start or may drop out during compressor start.
|
Low Line Voltage / Brownout Condition | View Details |
| E430 |
Lennox thermostat shows E430 indoor humidity sensor error; dehumidification features may not work correctly during cooling.
|
Indoor Humidity Sensor Fault | View Details |
| E440 |
Lennox communicating system shows E440 indoor unit configuration or model mismatch error; system may not operate or may run in backup mode.
|
Configuration / Model Mismatch Fault | View Details |
| E441 |
Lennox thermostat shows E441 outdoor unit configuration error; outdoor unit may not respond correctly to staging commands.
|
Outdoor Unit Configuration Fault | View Details |
| E450 |
Lennox system shows E450 condensate overflow or float switch error; cooling is disabled even though thermostat is calling.
|
Condensate Overflow Protection Trip | View Details |
| E460 |
Lennox thermostat shows E460 indoor coil sensor out of range; system may shut down or run with limited capacity.
|
Indoor Coil Temperature Sensor Fault | View Details |
| E470 |
Lennox system reports E470 compressor overload or thermal protection trip; compressor shuts off and may restart after cooling down.
|
Compressor Overheating / Overload Trip | View Details |
| E480 |
Lennox communicating system shows E480 compressor short-cycling or minimum off-time violation; compressor starts and stops frequently.
|
Compressor Short Cycling Protection | View Details |
| – |
Lennox air conditioner causes lights to dim or flicker in the home when the compressor starts.
|
High Inrush Current / Voltage Sag | View Details |
| – |
Lennox air conditioner cycles normally but humidity in the home remains high and feels clammy.
|
Poor Dehumidification Performance | View Details |
| – |
Lennox air conditioner emits a burning or electrical smell when running.
|
Overheating Electrical Component or Dust Burn-Off | View Details |
| – |
Lennox air conditioner frequently freezes the indoor coil; ice forms on refrigerant lines and coil housing.
|
Evaporator Coil Freeze-Up | View Details |
| – |
Lennox air conditioner indoor blower runs but outdoor unit does not; room temperature rises and no heat is removed.
|
Outdoor Unit Control Circuit Open | View Details |
| – |
Lennox air conditioner makes loud buzzing or humming at the outdoor unit when trying to start, but fan and/or compressor do not run.
|
Failed Capacitor or Stalled Motor | View Details |
| – |
Lennox air conditioner outdoor unit runs but indoor blower does not; suction line may ice up and little or no air comes from vents.
|
Indoor Blower Non-Operation | View Details |
| – |
Lennox air conditioner outdoor unit runs in cold weather when it should be off (for cooling-only systems).
|
Stuck Contactor or Control Logic Fault | View Details |
| – |
Lennox air conditioner produces a musty or moldy smell when it starts, especially after being off for a while.
|
Biological Growth on Evaporator Coil or Drain Pan | View Details |
| – |
Lennox air conditioner runs but does not cool well; supply air is only slightly cooler than room temperature.
|
Insufficient Cooling Capacity | View Details |
| – |
Lennox air conditioner runs continuously and struggles to reach set temperature on very hot days.
|
Capacity or Airflow Deficiency | View Details |
| – |
Lennox air conditioner short cycles, turning on and off every few minutes without reaching set temperature.
|
Short Cycling Due to Control or Sizing Issues | View Details |
| – |
Lennox air conditioner thermostat display is blank or unresponsive; system does not run.
|
Thermostat Power Loss | View Details |
| – |
Lennox outdoor unit frequently trips the breaker when starting or during operation.
|
Overcurrent / Short Circuit | View Details |
| – |
Lennox outdoor unit is excessively noisy during operation, with rattling, vibrating, or metallic banging sounds.
|
Mechanical Vibration or Fan Imbalance | View Details |
| – |
Outdoor Lennox air conditioner unit will not turn on at all; indoor blower runs and thermostat appears normal but condenser is silent.
|
Outdoor Unit Power or Contactor Failure | View Details |
| – |
Outdoor Lennox condenser fan runs but compressor does not start; unit hums or is unusually quiet and no cooling is produced.
|
Compressor Start Failure | View Details |
| – |
Water leaking from Lennox indoor air handler or furnace cabinet during cooling; puddles form around the unit.
|
Condensate Drainage Failure | View Details |
No matching codes found
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