Furnace Not Heating in Moraga
A furnace that won't heat is rarely a dead system. Every cycle, the igniter has to glow, the gas valve has to open, the flame sensor has to confirm the burn, and the inducer and limit switch have to allow it. One failed part stops heat cold. The repair is usually a single component, and we find which one before quoting anything.
Moraga sits in a valley that gets cool, foggy mornings and warm afternoons, the kind of damp chill that has people reaching for the thermostat and finding the furnace won't fire. A lot of homes here are 1960s through 80s ranches on larger hillside lots, and many of those original furnaces are at or past the 25-year mark. That age brings predictable failures: cracked igniters, worn inducers, limit switches tripped by neglected filters, and the occasional cracked heat exchanger.
Winters are mild enough that a no-heat call isn't an emergency, though a cold house gets uncomfortable fast in the morning damp. It's also the right age of equipment to take the CO test seriously, which we do on every gas call.
Common causes
Cracked hot surface igniter. The most common no-heat failure on furnaces of this age. The igniter cracks from years of cycling and the burners never light. We confirm with a resistance test and replace it. The exact part cost goes on your written estimate.
Limit switch tripped by a dirty filter. On older ranch furnaces with a long-neglected filter, restricted airflow overheats the unit and trips the high-limit, shutting the burners off. We replace the filter, check static pressure, and confirm the reset. If the ductwork is part of the airflow problem we note it on the estimate.
Worn draft inducer motor. On furnaces past about a decade, the inducer that vents combustion gases wears out. Without proper draft the pressure switch won't let the furnace fire. We confirm the inducer and pressure switch before quoting, and the inducer is one of the larger repair line items, which we'll spell out for you.
Flame sensor carbon buildup. The furnace lights, then dies after a few seconds. A fouled flame sensor stops the board from confirming the burn, so it cuts gas. Cleaning the rod usually fixes it. A worn sensor that needs replacing is a small part we'll price first.
Cracked heat exchanger. Furnaces at the 25-year mark common in Moraga are the right age to crack a heat exchanger, which is a carbon monoxide hazard. We inspect with a camera and show you any crack before quoting. If CO is dangerous we shut the unit down and leave you the documentation.
Failed control board. After two decades of heat cycling, a control board can start giving intermittent no-heat cycles. We meter the board outputs through a full cycle to confirm it before replacing, since a loose connection or corroded terminal can mimic a board fault.
How we diagnose it
- Confirm the thermostat is calling and the furnace board is getting the heat signal.
- Run a full ignition cycle to locate exactly where heat stops.
- Inspect and replace the filter, then check static pressure for airflow-driven limit trips on these older systems.
- Verify draft inducer and pressure switch operation, common wear points past a decade.
- Test CO and inspect the heat exchanger on every gas furnace before sign-off.
$75 diagnostic, credited toward any repair over $200. You get a written quote before any work begins.
Furnace Not Heating in Moraga: common questions
Do you come out to Moraga, or is it too far off the beaten path?
My furnace is past 25 years. Repair the no-heat fault or replace?
The furnace won't fire at all on cold mornings. What's going on?
Nearby and related
Furnace Not Heating near Moraga: Orinda · Lafayette .
This is usually a furnace repair in Moraga job. See our furnace repair overview or the Moraga service area.
Furnace Not Heating in Moraga
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