Most Lennox equipment in San Jose homes is part of a ducted system: a gas furnace or air handler with an indoor coil, and an air conditioner or heat pump outside. Many of these systems also have an iComfort thermostat, and some have a PureAir air cleaner in the return duct. When something goes wrong, the thermostat or the air cleaner is often where you notice it first, even when the fault sits somewhere else.
What Lennox sells
Lennox makes gas furnaces, including high-efficiency condensing models, central air conditioners, heat pumps, air handlers and coils, and ductless mini-splits. It also sells its own thermostats under the iComfort name and indoor air quality products such as the PureAir air purification system. Some Lennox systems from past years were sold with SunSource, a solar option tied to the outdoor unit; if yours has it, mention it when you book so the technician knows what to expect.
When the thermostat is part of the system
Some iComfort thermostats are smart thermostats on standard wiring. Others communicate with iComfort-enabled furnaces, air handlers and outdoor units, and show the equipment’s alert codes on screen. In practice:
- A blank screen is not proof of a dead thermostat. The thermostat takes its power from the indoor unit. A tripped breaker, a furnace door switch left open or a blown fuse on the control board leaves the screen dark too. We check the power path before ordering anything.
- An alert code is a lead, not a verdict. Photograph it along with the time it appeared. A communication alert can come from a loose wire at either unit, which is a much smaller job than a failed board.
Thinking of swapping the Lennox thermostat for another brand? Ask first: on a communicating system, a different thermostat may not run the equipment’s staged or variable-speed features. See thermostat installation.
PureAir and other add-ons
A PureAir unit combines a dense media filter with ultraviolet lamps, and both wear out: the lamps lose output with age and the media fills with dust. An overdue filter cuts airflow through the whole system, which can freeze the indoor coil on a hot afternoon and trip the furnace’s limit switch in winter. Replace the media and lamps on the schedule in the owner’s manual, switch the power off before opening the cabinet, and never look straight at a lit UV lamp. Our air purification page covers whole-house air cleaning.
What fails and what gets checked
| What you notice | What we look at first |
|---|---|
| Water near a high-efficiency furnace | Condensate trap, drain line and pump; the same clog can stop the furnace |
| Furnace starts, then shuts down | Flame sensor, igniter, pressure switch, and the vent and intake pipes |
| Outdoor unit silent on a hot day | Breaker, disconnect, contactor and the low-voltage wiring |
| Long run times, upstairs rooms stay warm | Filter, PureAir media, coil condition and leaky ducts |
| Communication alert on the iComfort screen | Wiring and terminals at each unit before any board |
Warranty records
Lennox coverage depends on the model, the installation date and whether the equipment was registered in time; the warranty document gives the deadline. Keep the serial numbers of the furnace or air handler, coil, outdoor unit and thermostat, the installation invoice and the registration confirmation. Keep receipts for PureAir media and lamps and for yearly service as well, since a claim can ask how the system was looked after. The manufacturer’s coverage is for parts; the work to install them is a separate charge. We are independent and not connected to Lennox.
Repair or replace
Drains, sensors, igniters, capacitors and wiring faults are repairs. A failed compressor or inverter drive on an older variable-speed outdoor unit, or a cracked heat exchanger, is when replacement deserves a written comparison. Estimates for replacement systems are free. If you are weighing Lennox against another brand for a new system, our Lennox vs Carrier comparison covers what to check.
Local notes: Almaden Valley
Many Almaden Valley homes are larger, some over 3,000 square feet, and sit between the warmer valley floor and the cooler hillsides. A single Lennox system there can leave upstairs rooms warm on summer afternoons while the ground floor is comfortable, and owners often care about energy costs and whole-house air cleaning. Before adding equipment, we check duct sizing, return air and the PureAir filter, since a restriction at any of these can make a capable system look undersized.