HVACopediaLennox · Furnace troubleshooting
Two horizontal lines on display (soft disable) - Lennox communicating
What is going on
The control shows two horizontal lines on its 7-segment display (damper module or EIM: green LED 3 s on / 1 s off). The thermostat found a device it does not recognize and put it in soft disable; the thermostat itself shows no alert code for this (often alert 10 is logged).
Likely causes
- Control board was replaced and the system was not reconfigured
- New device added after commissioning
- Device on the bus not communicating with the thermostat
Check in this order
- Confirm wiring between all devices (thermostat/smart hub, indoor, outdoor, damper module, EIM).
- Cycle power to the control that shows the soft disable.
- Reconfigure. S30: go to Menu > Settings > Advanced Settings, open View Dealer Control Center, then Equipment > Reset All Equipment. S40: go to Menu > Settings > Advanced Settings, open View Service Support Center, then Equipment Setting > Reset and pick Reset HVAC Equipment.
- Run the thermostat setup again so it auto-detects every device.
- Check the device's installation/setup guide if it stays disabled.
Applies to: Lennox communicating gas furnaces (e.g. SL280UHV/SL280UHNV, EL296UHV) in S30/S40 smart thermostat systems
More furnace guides
- Blower motor does not run - Lennox SL280UHV ECM checks
- Display shows two horizontal bars (soft disable) - Lennox SL297NV
- EL296UHV: normal gas heat sequence (what should happen after a call for heat)
- EL296UHV: what the display and the diagnostic button are telling you
- Furnace will not run (no heat) - Lennox EL195UHNE
- Furnace will not run (no heat) - Lennox SL297NV
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Source: Lennox Alert Code Guide (V2) 100017, 3. Soft Disable, p.6; Lennox SL280UHNV Unit Information Corp 1601-L8 (rev 04/2024), Soft Disable, p.15. Written in our own words; check the manual for your exact model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.