HVACopediaLennox · Air handler
500 PureAir differential pressure sensor fault
What the control is telling you
Pressure sensor shows a fault or stays silent over 5 minutes, so filter life can't be worked out (remaining life reads '-'). S30/S40 alert code 500.
Applies to: Lennox communicating air handlers and EIM-equipped indoor units in S30/S40 smart thermostat systems
Likely causes
- PureAir S accessory issue
Test and repair steps
- Check the sensor wiring and connections.
- Replace the sensor if it does not recover.
- Clears 30 seconds after recovery.
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Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.44. Summarized in our own words; check the original manual for your model.
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