The short answer
PrimeAir HVAC Repair Service repairs gas furnaces in Foster City homes, from ignition and airflow problems to short cycling and odd noises, and offers 24/7 emergency service. Bay Area Air District rules do not require you to replace a working furnace, so repair is often the right first step when the equipment is otherwise in good shape.
When the furnace stops working on a cold, damp Foster City evening, you want a clear answer about what went wrong and what it will take to fix it. PrimeAir HVAC Repair Service sends technicians from our Fremont base, about 11 miles east, to homes throughout Foster City and the 94404 ZIP code. We diagnose the actual cause, explain your options in plain terms, and make the repair when it makes sense. We'll also tell you honestly when a furnace is near the end of its life, and how current Bay Area rules affect that decision.
Furnace problems we commonly fix in Foster City homes
Foster City winters are mild, so many furnaces sit idle for months and then get called on during a chilly, wet stretch. That on-and-off pattern means problems often show up on the first cold night of the season. Dust settles on burners and sensors over the summer, filters get forgotten, and small issues that went unnoticed last year become a no-heat call.
These are the symptoms homeowners describe to us most often:
- The furnace runs but blows cool or lukewarm air
- The system won't start, or the igniter clicks without lighting
- Short cycling, where the furnace turns on and off every few minutes
- Weak airflow from some or all vents
- Banging, rattling, squealing, or humming from the unit
- A burning smell that lingers past the first few minutes of the season
- The thermostat calls for heat but nothing happens
What happens during a repair visit
Our technician starts by asking what you've noticed and when it began. Then we check the furnace step by step: thermostat signal, power and safety switches, the ignition system and flame sensor, burners, the inducer and blower motors, the filter and airflow, and the venting. A furnace that shuts itself off is often responding to a safety switch, so we look for the reason it tripped instead of just resetting it.
Before any work begins, we explain what we found and what we recommend, and you decide how to proceed. Many repairs, such as a dirty flame sensor, a failed igniter, a worn blower capacitor, or a clogged filter restricting airflow, can be handled on the first visit when the part is on hand. If we smell gas or find signs of a cracked heat exchanger or a venting problem, we'll explain the safety concern and shut the unit down until it's corrected.
Repair or replace? What the Air District rules mean for you
Foster City is in San Mateo County, which falls under the Bay Area Air District. Under the district's Rule 9-4, natural gas furnaces manufactured from 2029 on must meet a zero-NOx emission standard. In practice, that points homeowners toward heat pumps when a furnace is replaced after that date.
That rule does not require you to replace working equipment. It applies only when an existing furnace fails or is replaced. If your furnace is sound and the repair is reasonable, fixing it keeps your home warm without forcing a bigger decision before you're ready.
When a furnace is older, needs frequent repairs, or has a serious failure, we'll talk through both paths: one more repair, or planning a replacement. If a heat pump is on the table, we can explain how it would heat and cool your home and what the switch would involve.
Incentives and tax credits to know about
The federal Energy Efficient Home Improvement Credit (25C) covered qualifying heat pumps placed in service before December 31, 2025. It is not available for new installations after that date, so don't plan a replacement around it.
Bay Area homeowners can still check BayREN and their local clean energy provider for current heat pump and electrification incentives. Amounts and availability change by funding cycle, so we confirm the current offer before including it in any quote.
If you're also thinking about your water heater, the zero-NOx date for small water heaters under the Air District's Rule 9-6 was set for 2027. The Air District Board is considering amendments in November 2026 that could delay it, so check the current rule before planning that replacement.
Emergency furnace service in Foster City and nearby
Furnaces don't always fail at convenient times, so we offer 24/7 emergency service for Foster City homes. If you have no heat, a furnace that won't stay lit, or anything that seems unsafe, reach out and we'll get a technician on the way.
Beyond Foster City, we also repair furnaces in Redwood City, San Carlos, Atherton, Menlo Park, and Hayward, along with our home area around Fremont.
More services in Foster City
- AC Repair in Foster City
- Heating Repair in Foster City
- Heat Pump Installation in Foster City
- AC Installation in Foster City
