Lennox Error Code E124: Thermostat lost communication to smart hub (Air Handler)
Lennox error code E124 on a air handler means: Thermostat lost communication to smart hub. It is also called Lennox diagnostic code E124.
Homeowner? What Lennox code E124 means for you
Call a technician Your air handler is reporting: Thermostat lost communication to smart hub. The air handler has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.
Safe things you can check yourself
- Check the thermostat: right mode (Heat or Cool), set a few degrees past room temperature, and fresh batteries if it uses them.
- Make sure the unit has power: its on/off switch (often looks like a light switch near the unit) is ON and the breaker in the electrical panel is not tripped.
- Look at the air filter. If it is grey and clogged, replace it; a blocked filter causes many shutdowns.
- Try one reset: turn the power off for 30 seconds, then back on. If the code comes back, stop resetting and call a technician.
Call (647) 657-2977Book a service call
Licensed technicians serving Vaughan, Toronto and the GTA.
What does Lennox error code E124 mean?
The thermostat has lost communication with a component for more than three minutes; all related operation stops until it hears from that component. S30/S40 thermostat alert code 124 (shown as E124 on the unit control display).
Applies to: Lennox communicating air handlers and EIM-equipped indoor units in S30/S40 smart thermostat systems
Common causes of Lennox code E124
- Loose or miswired communication wires
- A miswired component causing false codes
- Float switch wiring
Other Lennox Air Handler codes
All Lennox Air Handler error codes →
Lennox code E124: homeowner questions
What does Lennox code E124 mean?
Thermostat lost communication to smart hub. The thermostat has lost communication with a component for more than three minutes; all related operation stops until it hears from that component. S30/S40 thermostat alert code 124 (shown as E124 on the unit control display).
Is it safe to keep using my air handler with code E124?
It depends on the cause. The air handler has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.
Can I reset Lennox code E124 myself?
You can try one reset (power off for 30 seconds, then on). If Lennox code E124 comes back, the cause is still there and a licensed technician should check it.
Who can fix Lennox code E124 near me?
Aurora Star Tech Inc. repairs Lennox air handlers in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.
Troubleshooting guides
- Two horizontal lines on display (soft disable) - Lennox communicating Lennox · Air Handler
Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.17. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.