Lennox and its sister brands
Lennox International sells the Lennox brand directly to dealers, and also owns Allied Air, which builds Armstrong Air, Ducane and AirEase. Those brands share a lot of parts and design. Lennox model lines run from Merit (basic) to Elite to Signature (top of the line, including variable speed units).
The most common Lennox AC problems
- Fan not spinning, unit humming. Run capacitor or fan motor, the most frequent summer repair on any brand.
- No cooling, thermostat looks normal. Contactor, breaker, low voltage fuse, or the drain safety switch.
- iComfort alert on the screen. Signature and many Elite systems with an iComfort thermostat report problems as numbered alerts. Take a photo of the screen. The code tells the technician where to start.
- Variable speed unit stops or runs slowly. Lennox inverter models (for example the SL28XCV and XC25) depend on an inverter control board and sensors. Diagnosis takes proper tools, so do not keep power cycling it.
- Water leaking indoors. Clogged condensate line or a full secondary pan. Shut the system off if water is reaching the ceiling.
What you can safely check yourself
- Thermostat on Cool, set below room temperature, schedule not overriding you.
- Replace the filter. Lennox systems often use thick media filters in a cabinet next to the furnace; those still clog.
- Check the breaker and the outdoor disconnect.
- Clear the area around the outdoor unit and rinse the coil gently with power off.
- If the lines are iced, switch the system off and run the fan only until it thaws.
Electrical parts and refrigerant are technician work. Capacitors and inverter boards store dangerous voltage.
Parts and timing on Lennox repairs
Because Lennox sells through its own dealer network, some model specific parts, such as inverter boards and certain motors, are not stocked at every supply house. Common parts like capacitors, contactors and many motors are available the same day. For a specialty part we tell you up front how long it will take, and we can often keep the system running in the meantime if it is safe.
Refrigerant on Lennox systems
Older Lennox units use R-22. Most units from about 2010 to 2024 use R-410A, and new Lennox systems use R-454B. A low charge always means a leak. We locate and repair the leak before charging, so you are not paying for the same refrigerant again next summer.
Repair or replace a Lennox AC?
On a single or two stage Lennox under about 12 years old, most repairs are worth doing. On a variable speed unit out of warranty, an inverter board or compressor failure can cost a large share of a new system, so we lay out both options in writing. On R-22 systems with a major failure, replacement is usually the smarter spend.
