Lennox Error Code E440: Inverter compressor slowdown – high heat-sink temperature (inverter code 13) (AC)
Lennox error code E440 on a air conditioner means: Inverter compressor slowdown - high heat-sink temperature (inverter code 13). It is also called Lennox diagnostic code E440.
Homeowner? What Lennox code E440 means for you
Usually minor Your air conditioner is reporting: Inverter compressor slowdown - high heat-sink temperature (inverter code 13). This code is usually informational or minor. The safe checks below often clear it; call us if it keeps showing up.
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.
- Check both breakers and the outdoor disconnect box beside the outdoor unit; all should be ON.
- Look at the air filter. If it is grey and clogged, replace it; a blocked filter causes many shutdowns.
- Keep about 2 feet around the outdoor unit clear of leaves, grass and debris.
- If you see ice on the pipes or the indoor coil, turn the system off and run only the fan for a few hours, then call a technician.
- 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 E440 mean?
Heat sink near its limit; the compressor slows (about 4 Hz, 5-6%) to cool it. Speed reduction starts above 185 F and full speed resumes at 176 F. Normal for 3-4 minutes above 110 F outdoor (dealer information). Inverter LED flash code 13 (red 1 flash, green 3 flashes). S30/S40 thermostat alert code 440 (shown as E440 on the unit control display).
Applies to: Lennox communicating air conditioners incl. variable-capacity inverter units in S30/S40 smart thermostat systems
Common causes of Lennox code E440
- High outdoor temperature
- Debris on heat sink
- Loose heat sink screws
Lennox models that use code E440
EL16KC1-018-230AEL16KC1-024-230AEL16KC1-030-230AEL16KC1-036-230AEL16KC1-041-230AEL16KC1-042-230AEL16KC1-047-230AEL16KC1-048-230AEL16KC1-060-230A
Other Lennox AC codes
All Lennox Air Conditioner error codes →
Lennox code E440: homeowner questions
What does Lennox code E440 mean?
Inverter compressor slowdown - high heat-sink temperature (inverter code 13). Heat sink near its limit; the compressor slows (about 4 Hz, 5-6%) to cool it. Speed reduction starts above 185 F and full speed resumes at 176 F. Normal for 3-4 minutes above 110 F outdoor (dealer information). Inverter LED flash code 13…
Is it safe to keep using my air conditioner with code E440?
Usually yes. Code E440 is normally minor, but if it keeps coming back have it checked.
Can I reset Lennox code E440 myself?
You can try one reset (power off for 30 seconds, then on). If Lennox code E440 comes back, the cause is still there and a licensed technician should check it.
Who can fix Lennox code E440 near me?
Aurora Star Tech Inc. repairs Lennox air conditioners in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.
Homeowner help: AC Running But Not Cooling: What to Check
Troubleshooting guides
- Not cooling All brands · Air Conditioner
- Low cooling capacity - check airflow and charge - Lennox EL16KC1 Lennox · Air Conditioner
- Outdoor unit will not start - Lennox EL16KC1 Lennox · Air Conditioner
- RDS leak-detected mode and start-up test - Lennox EL16KC1 Lennox · Air Conditioner
- Two horizontal lines on display (soft disable) - Lennox communicating Lennox · Air Conditioner
Source: Lennox Residential Communicating Systems Alert Code Guide (V2) 100017 (3/2023), Table 2 Alert Codes and Troubleshooting, p.42. 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.