Lennox furnaces post the highest efficiency numbers in the category, and they fail in the same predictable SoCal pattern as any gas furnace — almost always an inexpensive single-visit fix. This page is the Lennox-specific companion to our general furnace repair service and our Lennox brand overview.
Common Lennox furnace failures, by model
From years of Lennox service calls, the no-heat failures cluster predictably:
- Hot-surface ignitor wear — the most common Lennox no-heat call. The silicon-nitride ignitor degrades over hundreds of cycles and eventually cracks. Symptom: blower runs, no flame. $245–$485 installed.
- Flame-sensor fouling — the furnace lights, then shuts down after 3–7 seconds because a dust-coated sensor cannot prove flame. Clean or replace, $185–$295.
- Draft-inducer motor failure on SL280V and EL296V furnaces in years 8–12 — a pressure or venting code, or a furnace that never starts the ignition sequence. $580–$1,100, warranty-covered on the part if registered.
- Integrated control-board failure — frequently after a Santa Ana voltage transient. $480–$950.
- Pressure-switch and venting faults — a blocked condensate trap on a 90%+ condensing furnace or a sagging vent keeps the pressure switch from closing. Diagnosed at the $89 visit.
- Heat-exchanger cracks on older 1990s–2000s Pulse and G61 furnaces — a safety condemnation and replacement, not a repair.
Reading the Lennox fault code
How a Lennox furnace reports a fault depends on its generation. Communicating furnaces (SL280V, SL297NV, EL296V on the iComfort platform) display an alphanumeric alert code on the iComfort S30 thermostat, logged with a timestamp under Settings and Diagnostics. Older and conventional furnaces flash a diagnostic LED on the control board, viewed through the inspection port. Either way the code points to a subsystem, not a specific failed part. We read it, confirm it on the meter, and name the part. The full code reference is on our Lennox error codes page, and the airflow-and-limit chain is in our furnace short-cycling guide.
Why Lennox furnaces fail when they do in SoCal
An LA-basin furnace runs 200–500 hours a year against 1,500-plus in a cold climate. That long idle stretch from April to October is where the trouble breeds: dust cakes the flame sensor, the ignitor ages without being exercised, inducer bearings stiffen, and control-board capacitors drift. The first November cold snap then asks an untouched furnace to fire cleanly, and the predictable failures surface all at once. Mountain installs in Big Bear and Wrightwood run real heating hours and fail on a different curve — more wear, fewer idle-related faults. Either way, fall maintenance in October is the cheapest insurance; the cold-air and ignition chains are walked through in our furnace blowing cold air, furnace ignitor failure, and pilot light won’t stay lit guides.
Lennox furnace repair pricing
Flat-rate, parts and labor, from our SoCal service tickets. Diagnostic is $89 ($149 after-hours), credited to the repair if you proceed:
| Lennox furnace repair | Typical cost |
|---|---|
| Diagnostic (waived with repair) | $89 / $149 after-hours |
| Hot-surface ignitor | $245–$485 |
| Flame sensor (clean or replace) | $185–$295 |
| Gas valve | $385–$685 |
| Blower motor | $480–$890 |
| Integrated control board | $480–$950 |
| Draft inducer motor (SL280V / EL296V) | $580–$1,100 |
| Heat exchanger (crack — we quote replacement) | $1,500–$3,500 |
Lennox heat exchangers on Signature and Elite furnaces carry a lifetime warranty to the original owner; other parts are 5 years, extendable to 10 with registration within 60 days. Labor is separate. We look up registration before ordering.
Repair or replace your Lennox furnace
Under 10 years old with a repair under roughly a third of replacement cost, repair it — an SL280V with a failed inducer at year 9 has plenty of cabinet and heat-exchanger life left. Over 15 years, or any age with a cracked heat exchanger, replace it: a cracked exchanger is a carbon-monoxide path, and we red-tag and shut the gas before leaving. The 10-to-15-year window is judgment, and we give you the repair figure and a written replacement quote side by side. See furnace installation when replacement is the call, and our honest framing on furnace repair vs. replace.
iComfort and older Lennox furnaces
We service both the current iComfort-communicating furnaces and older conventional Lennox units. For the cooling side of a Lennox system, see Lennox AC repair, a no-heat walkthrough on Lennox furnace not heating, and the full lineup on our Lennox brand page.