Lennox SLP98UHV Error Code E 180: Outdoor Air Sensor Failure
What Does Code E 180 Mean?
Error code E180 on the Lennox SLP98UHV indicates an outdoor air sensor failure. The sensor is either shorted or reading a value outside the expected range. Notably, this error only appears for shorted or out-of-range conditions — if the sensor is simply disconnected, no error is generated.
The outdoor air temperature sensor provides data that the control board uses to optimize the furnace's variable-capacity operation. By knowing the outdoor temperature, the system can anticipate heating load and adjust its firing rate proactively. Without this data, the furnace relies solely on indoor temperature feedback, which means it may be slightly less responsive to changing conditions.
The furnace will continue to operate normally for heating, so this is not an urgent repair. However, a technician should compare the sensor's resistance to the temperature/resistance chart in the installation instructions to confirm the sensor has failed, and replace it to restore full system optimization.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Outdoor temperature sensor shorted or wiring damaged | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- The outdoor temperature sensor needs to be tested and replaced
- You want to restore the system's outdoor temperature-based performance optimization
- The sensor wiring may be damaged and needs inspection
✓ Verified against manufacturer service manual — March 2026