HVACopediaLennox · Air handler
Green LED 3 s on / 1 s off Soft disable - zoning damper module or EIM
What the display is showing
On a Smart Zoning damper control module or an equipment interface module (EIM), the green LED blinks 3 seconds on and 1 second off. The thermostat found a device on the communication bus that it does not recognise and has parked it in soft disable until it is configured or removed. The thermostat itself shows no alert code for this; only the affected control shows the indicator. Often seen after a control is replaced.
Applies to: Lennox S30/S40 communicating systems: communicating furnaces, air handlers, outdoor units, Smart Zoning and EIM
What to do
- Check the wiring between thermostat, indoor and outdoor units.
- Cycle power to the control showing the indicator.
- Re-run the system configuration on the thermostat so the new control is learned.
- If the thermostat raised alert 10, clear it after the system is reconfigured.
Save it for the next call
Star this code in the HVACopedia app and keep the whole library on your phone for jobs with no signal.
Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), 3. Soft Disable, p.7; Table 2 alert code 10, p.8. Summarized in our own words; check the original manual for your 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.