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Lennox · Air conditioner 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

  1. Confirm wiring between all devices (thermostat/smart hub, indoor, outdoor, damper module, EIM).
  2. Cycle power to the control that shows the soft disable.
  3. 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.
  4. Run the thermostat setup again so it auto-detects every device.
  5. Check the device's installation/setup guide if it stays disabled.

Applies to: Lennox communicating air conditioners incl. variable-capacity inverter units in S30/S40 smart thermostat systems

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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.