Lennox SLP98UHV Error Code d: Dehumidification Mode
What Does Code d Mean?
The lowercase letter d on the Lennox SLP98UHV display indicates the dehumidification mode diagnostic readout. This appears as part of the diagnostic menu cycle when the push button on the control board is pressed. The display shows the blower CFM setting used during dehumidification operation.
The SLP98UHV can operate in a dehumidification mode when paired with a compatible iComfort thermostat that has humidity control. In this mode, the blower runs at a lower speed than normal cooling to allow the evaporator coil to remove more moisture from the air. The d readout shows what that reduced airflow setting is.
This is purely informational and requires no action. The display will continue cycling through other diagnostic items or return to idle. If you are experiencing humidity issues in your home, the dehumidification settings may need adjustment by a technician through the thermostat configuration.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Diagnostic push button pressed to view dehumidification settings | Most common | — |
When to Call a Professional
Contact a licensed HVAC technician if:
- Your home feels too humid even with the system running in dehumidification mode
✓ Verified against manufacturer service manual — March 2026