Furnace Not Heating in San Mateo, CA

Furnace Not Heating in San Mateo

No heat from a gas furnace almost always traces to one step in the ignition sequence failing. The inducer has to run, the igniter has to glow or spark, the gas valve has to open, and the flame sensor has to confirm the flame is lit, and a fault at any one of those steps shuts the whole cycle down as a safety measure. Add a tripped limit switch from restricted airflow, a dead thermocouple on an older wall or gravity furnace, or simply no call for heat reaching the board, and that covers nearly every no-heat call we run. We watch the sequence directly rather than swapping parts on a guess. The detail that matters in San Mateo is the mix of condos and townhomes alongside older single-family neighborhoods.

Housing age and local climate both matter on a no-heat call. San Mateo is the biggest city on this stretch of the Peninsula and runs a real mix of microclimates, from the cooler bayfront near Foster City to the warmer hills around San Mateo Park and the Highlands. The city has more condos and townhomes than most of its neighbors, concentrated around Hillsdale and North Central, alongside older single-family neighborhoods like Baywood and San Mateo Park with original HVAC well past service life. A condo or townhome job usually means a packaged or ductless system and an HOA to coordinate with, a different conversation than a single-family install.

In San Mateo, every gas furnace call includes a carbon monoxide reading and a heat exchanger check, regardless of what brought us out, because that's a safety step we don't skip. The written estimate covers the actual repair, and on an older furnace we'll tell you honestly whether a heat pump conversion is worth putting on the table too. The $99 diagnostic fee is credited toward the repair.

Common causes

Cracked hot surface igniter. The igniter is a thin ceramic element that eventually cracks from repeated heating and cooling cycles. Once it can no longer glow hot enough, the gas valve never gets confirmation to stay open.

Dirty flame sensor. A flame sensor coated with a thin layer of carbon can no longer read the flame properly, so the board shuts the gas valve seconds after ignition, over and over, until the furnace locks out.

Limit switch tripped by a dirty filter. Restricted airflow, often from a dirty filter, lets the heat exchanger run hotter than it should and trips the high-limit switch as a safety response, shutting the burners down. Condos and townhomes here usually run shorter, simpler duct runs than a house, though any restriction shows up faster in that smaller space.

Failed thermocouple on a wall or gravity furnace. Older wall and gravity furnaces use a thermocouple rather than a flame sensor, and a weakening one shuts the pilot's gas valve even when the pilot is actually lit.

Corroded gas valve or board connection. Age and moisture take a toll on gas valve terminals and board connectors over time. Hillsdale-area condos and townhomes commonly run packaged or through-wall equipment with more exposed wiring than a house. That can cause an intermittent or complete no-heat fault.

Thermostat or no call for heat. If the call for heat never reaches the board, nothing downstream matters yet. We confirm 24 volts and a real heat call reach the furnace before assuming a mechanical failure.

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. Hillsdale-area condos and townhomes commonly run packaged or through-wall equipment with more exposed wiring than a house. Condos and townhomes here usually run shorter, simpler duct runs than a house, though any restriction shows up faster in that smaller space.

$99 diagnostic, credited toward the repair. You get a written quote before any work begins.

Furnace Not Heating in San Mateo: common questions

Do you serve San Mateo, and how quickly can you get to a no-heat call?

Yes. We're based in San Ramon and cover the Peninsula including San Mateo, Burlingame, and Foster City. We dispatch the closest available tech and give you a realistic arrival window when you call, rather than a blanket promise we can't back up. Call (925) 999-4095.

We're in a condo near Hillsdale with a packaged unit, not a house with a normal system. Does that change how you handle it?

Yes, a bit. Condo and townhome systems around Hillsdale usually run packaged or through-wall equipment with different service access and wiring than a single-family home, and there's often an HOA to coordinate with on anything visible from outside. We handle that coordination as part of the visit rather than leaving it for you to sort out.

The furnace tries to start, clicks a few times, then gives up. What does that mean?

That clicking is usually the igniter or an ignition attempt that is not lighting the burners, and most furnace boards will lock out after three or so failed tries as a safety measure. It typically points to the igniter, the flame sensor, or the gas valve rather than something bigger, and we can usually confirm which one on the same visit.

Nearby and related

Furnace Not Heating near San Mateo: Burlingame · Belmont · Foster City .

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

Furnace Not Heating in San Mateo

Repairs start with a $99 diagnostic, credited toward the fix. Replacing a system? The on-site assessment visit is free. Same-day written findings either way.

Bay Area · 7am–7pm · 7 days · no overtime charges

(925) 999-4095 →

Furnace Not Heating in San Mateo