Furnace Not Heating in Alameda, CA | Bay Area HVAC Service

Furnace Not Heating in Alameda

A furnace that won't heat almost never means the whole system is dead. On a forced-air gas furnace it usually comes down to one part in the ignition or safety chain: a cracked hot surface igniter, a flame sensor coated in carbon, a limit switch tripping on a dirty filter, or a thermostat that lost its call for heat. The blower and the burners are separate jobs, so a unit that hums and pushes cold air is telling you something different than one that stays completely silent.

Alameda has a particular wrinkle here. A lot of the older island homes through the Gold Coast and Park Street never had central forced air. They run wall furnaces or old gravity heat, and those fail in their own ways: a clogged pilot orifice, a bad thermocouple, a stuck gas valve. Bay Farm Island is the newer side with conventional forced-air systems, where the failures look more like the standard igniter and flame-sensor story. We diagnose to the equipment in front of us, not a generic checklist.

The other thing worth naming on the island is salt air. The marine layer that keeps Alameda mild also corrodes contacts, gas valve terminals, and control board connectors faster than they corrode inland. A furnace that quit may have a clean part with a corroded connection feeding it, and that changes what goes on the estimate.

Common causes

Cracked hot surface igniter. On modern forced-air furnaces this is the single most common reason the burners never light. The igniter glows to ignite the gas, and after years of heat cycling it develops a hairline crack and stops glowing. We test it for continuity and resistance, and replacement runs $200 to $350 depending on the unit.

Dirty flame sensor. If the furnace lights for a few seconds then shuts off, the flame sensor is usually the culprit. Carbon builds up on the rod so the board can't confirm a flame and shuts the gas off as a safety measure. Cleaning often restores it; if the sensor is pitted we replace it, typically $150 to $200.

Limit switch tripped by a dirty filter. Alameda homes with the filter behind a wall return often go a long time between changes. A clogged filter chokes airflow, the heat exchanger overheats, and the high-limit switch shuts the burners down to protect it. We pull the filter, confirm airflow, and check whether the limit switch reset or failed closed.

Failed thermocouple on a wall or gravity furnace. On the island's older wall and gravity furnaces, the pilot won't stay lit when the thermocouple weakens. It stops generating the millivolts that hold the gas valve open. We test the output and replace the thermocouple, and at the same time we check the heat exchanger on these older units.

Corroded gas valve or board connection. Salt air gets into terminals and connectors. A furnace that quit can have a good part starved by a corroded connection or a gas valve coil that no longer pulls in cleanly. We check voltage at the valve and inspect the board harness before condemning expensive parts.

Thermostat or no call for heat. Sometimes the furnace is fine and the thermostat lost power, lost its wiring connection, or was set wrong. We confirm there's a real call for heat reaching the board before we open the burner compartment, because chasing the wrong end wastes your money.

How we diagnose it

Confirm a real heat call reaches the control board, so we're diagnosing the furnace and not a dead thermostat or broken low-voltage wire.
Watch a full ignition sequence: inducer, igniter glow, gas valve, flame sensing, and where in that chain it stops.
Test the igniter, flame sensor, and limit switch directly with meters rather than swapping parts on a guess.
On every gas furnace, meter carbon monoxide and inspect the heat exchanger; on older wall and gravity units this is non-negotiable.
Check filter, airflow, and the gas valve and board connections for the salt-air corrosion common on the island.

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

Furnace Not Heating in Alameda: common questions

Do you actually cover Alameda, or just the inland Tri-Valley?

We cover Alameda regularly, both the main island and Bay Farm. We're based in San Ramon and run the full Bay Area, and a no-heat call gets priority routing. Call (925) 999-4095 and we'll give you an honest arrival window rather than a vague all-day promise.

It barely gets cold here, so is a furnace repair even worth it?

Alameda winters are mild, but those low-40s nights still mean you want reliable heat, and a no-heat furnace is often a $200-something fix, not a replacement. The $75 diagnostic is credited toward any repair over $200. If your unit is old enough that we'd be sinking money into a dying system, we'll tell you that on the written estimate instead of upselling you.

My furnace turns on, then shuts off after a few seconds. What is that?

That short-cycle on ignition is the classic dirty-flame-sensor pattern: the burner lights, but the board can't confirm a flame and cuts the gas as a safety. Cleaning the sensor fixes it most of the time. If it isn't the sensor, the next suspects are the igniter, a flame-rollout or limit trip, or a grounding issue, and we test in that order.

Nearby and related

Furnace Not Heating near Alameda: Oakland · San Leandro · Berkeley .

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