Lennox Error Codes

Select an error code below to identify the problem and find the solution.

Disclaimer: This information is for general reference. Error codes can vary by model and production year. Always refer to your machine's specific manual and the information printed on the unit itself.

No Power

No Power. The furnace may not be receiving power. Check the breaker and fuse.

Slow Flash / Slow Flash

Blower Motor Fault (Normal Operation with Call for Heat)

Blower Motor Fault (Normal Operation with Call for Heat). If alternating, it may indicate a different issue, but simultaneous slow flash often means normal operation or blower issue depending on model. Consult manual.

Alt Slow Flash / Alt Slow Flash

Flame Failure / Watchguard Mode

Flame Failure / Watchguard Mode. The system has failed to ignite or lost flame signal multiple times.

On / Slow Flash

Limit Switch Open

Limit Switch Open. The furnace has overheated or the rollout switch has tripped.

Slow Flash / On

Limit Switch Open (Variant)

Limit Switch Open (Variant). The furnace has overheated or the rollout switch has tripped.

Slow Flash / Fast Flash

Low Flame Signal

Low Flame Signal. The flame sensor current is weak.

Fast Flash / Slow Flash

Polarity Reversed

Polarity Reversed. The incoming power polarity is reversed or there is a grounding issue.

Alt Fast Flash / Alt Fast Flash

Control Board Failure / Voltage Issue

Control Board Failure / Voltage Issue. The control board is not functioning properly or voltage is out of range.

Hard Lockout - Rollout Switch Open

Hard Lockout - Rollout Switch Open. The flame rollout switch has detected flames outside the heat exchanger.

Lost Communication with Indoor Blower

Lost Communication with Indoor Blower. The control board cannot communicate with the blower motor.

Lost Communication with Outdoor Unit

Lost Communication with Outdoor Unit. The control board cannot communicate with the outdoor unit (communicating systems).

Low Pressure Switch Open

Low Pressure Switch Open. The low pressure switch is open (Cooling/Heat Pump).

High Pressure Switch Open

High Pressure Switch Open. The high pressure switch is open (Cooling/Heat Pump).

Flame Sensor Out of Sequence

Flame Sensor Out of Sequence. Flame sensed when gas valve should be closed.

Indoor Blower Motor Start Failure

Indoor Blower Motor Start Failure. The blower motor failed to start.

Reduced Airflow (Blower Speed)

Reduced Airflow (Blower Speed). The blower is running at a reduced speed to prevent damage.

Code Index

All Codes

207 Alt Fast Flash / Alt Fast Flash Alt Slow Flash / Alt Slow Flash E200 E201 E202 E223 E225 E241 E292 E312 Fast Flash / Slow Flash Off / Off On / Slow Flash Slow Flash / Fast Flash Slow Flash / On Slow Flash / Slow Flash