Furnace Not Heating in Lafayette

Furnace Not Heating in Lafayette

Lafayette sits in the Diablo Valley, moderated by the surrounding hills but cool enough in winter that the upper hillside lots see sub-freezing nights. When a furnace quits up there, the house loses heat quickly and the call comes in early. A lot of those homes are older mid-century construction running furnaces past their 20-year mark, and on equipment that old a no-heat failure is almost always a single worn component.

The hillside character also affects access. Furnaces and their flues run through tight crawl spaces and framed chases, and condensate and venting problems are more common here than in flat-tract neighborhoods. A blocked condensate line or a pressure switch that will not close on an aging inducer can lock the burners out and leave you with a fan running cold air.

A furnace that has heated reliably for two decades does not quit all at once. It loses one part, usually an igniter, a flame sensor, or a switch. We find the specific failure, and on furnaces approaching the end of their service life we always inspect the heat exchanger, because at that age a no-heat symptom occasionally points to a safety problem rather than a simple repair.

Common causes

Cracked hot surface igniter. The most common no-heat cause on Lafayette's older furnaces. The igniter cracks from years of heat cycling and stops glowing. We meter it for continuity and replace it, usually the same visit, with the part priced on the estimate first.

Fouled flame sensor. The burner lights and shuts off within seconds. A carbon-coated sensor cannot prove the flame and the control board cuts the gas. Cleaning usually restores heat. We replace it only if it is pitted past use.

Blocked condensate or pressure switch lockout. Lafayette's tight hillside crawl spaces make condensate clogs and venting restriction more common. A blocked drain or an inducer that cannot build pressure keeps the pressure switch open, and the burners never light. We trace the venting and condensate path, not the switch alone.

Limit switch tripped by a dirty filter. Restricted airflow overheats the heat exchanger and the limit switch shuts the burners off. We check the filter and blower, restore airflow, reset, and confirm the furnace completes a full cycle.

Failed draft inducer motor. On furnaces past 20 years the inducer motor is a frequent failure. If it will not spin up, the pressure switch stays open and the burners cannot light. We confirm before quoting the motor on the estimate.

Cracked heat exchanger. On a furnace near the end of its life, a no-heat or short-cycling complaint sometimes traces to a cracked heat exchanger, a carbon monoxide hazard. We inspect on camera and show you the crack before we quote anything. If confirmed, we shut the system down and discuss replacement.

How we diagnose it

• We watch a full ignition cycle to locate the failure: no igniter glow, flame then lockout, or burners lighting with a cold blower.
• Because Lafayette's tight access makes blockages and pressure-switch lockouts more common, we trace the venting and condensate path through the crawl space.
• The igniter, flame sensor, limit switch, and pressure switch each get metered instead of swapped on a guess.
• On any older furnace we inspect the heat exchanger on camera before quoting a repair.
• We run a carbon monoxide test and confirm a complete heat cycle before leaving.

$75 diagnostic, credited toward any repair over $200. You get a written quote before any work begins.

Furnace Not Heating in Lafayette: common questions

Nearby and related

Furnace Not Heating near Lafayette: Orinda · Moraga · Walnut Creek · Alamo .

This is usually a furnace repair in Lafayette job. See our furnace repair overview or the Lafayette service area.