The short answer
Furnace problems in Monte Sereno often show up on the first cold night, when dust, a weak igniter or a dirty flame sensor causes smells, noises or lockouts. BayPro diagnoses the cause, repairs it and checks combustion and venting before restoring heat.
Monte Sereno winters are mild by most standards, but evenings on the southwest edge of the valley cool off quickly, and damp stretches between storms make a working furnace more than a luxury. Many homes here have more than one furnace, or a single large unit in a basement, garage or attic that has been running for a long time. BayPro Heating & Cooling, about nine miles away in San Jose, repairs gas furnaces in Monte Sereno and the surrounding hillside communities. Below we cover the sounds and smells that signal trouble, what happens on the first cold night of the season, and how we approach repairs on older equipment.
The first cold night of the season
A furnace that sat idle since spring has collected dust on its burners and heat exchanger. The first time it fires, a faint burning smell for a few minutes is normal as that dust burns off. If the smell persists, smells electrical or comes with smoke, shut the furnace off and call.
That first start is also when a marginal part finally fails. A hot surface igniter with a hairline crack, a flame sensor coated over the summer or a pressure switch tube full of debris can all stop the furnace before it ever delivers heat. Scheduling a fall inspection in October lets us catch those problems in daylight rather than at night.
Sounds and smells, and what they mean
Furnaces give clues before they quit. Learning what they sound like when healthy helps you notice when something changes.
- A loud boom when burners light usually means delayed ignition, often from dirty burners or low gas pressure
- High-pitched squealing tends to come from a blower or inducer motor bearing, or a slipping belt on older units
- Rattling may be a loose panel, but on older furnaces it can also be a cracked heat exchanger and needs inspection
- Repeated clicking without ignition points to an igniter, gas valve or control board issue
- A rotten egg smell means a possible gas leak: leave the house and call the gas utility from outside
- A musty smell at startup can mean moisture in the ducts or a dirty filter
Larger homes and multiple furnaces
When a home has two furnaces, the one serving bedrooms or an upstairs level often works harder and fails first. Zoned single systems add dampers and a zone board that can malfunction independently of the furnace. We test each system and the controls between them, so a stuck damper is not mistaken for a furnace failure.
Basement and crawlspace furnaces deal with moisture that attic units do not. Rust on the burner box, corroded flame sensors and wet insulation around ducts are common. Garage furnaces need proper elevation and combustion air. We check those conditions on every visit because they affect how long a repair will last.
Safety checks on every repair
We inspect the heat exchanger for cracks and corrosion, verify the flue is intact and drafting properly, and test safety controls like the high limit and rollout switches. On high-efficiency furnaces we check the condensate trap and PVC vent connections. If we find a condition that could let combustion gases into the home, we will explain it clearly and recommend the furnace stay off until it is fixed.
Carbon monoxide alarms belong outside each sleeping area and on each level. If yours sounds, get everyone outside and call 911.
Repairing older furnaces and looking ahead
An older furnace that is well maintained can keep running reliably. We recommend repair whenever it makes practical sense and lay out replacement only when the heat exchanger is cracked, parts are unavailable or a major failure lands on a unit near the end of its life.
If replacement does come up, it helps to know the rules. Bay Area Air District Rule 9-4 requires gas furnaces manufactured from 2029 to meet a zero-NOx standard, which effectively points toward heat pumps for future replacements. The rule does not require you to replace a working furnace. BayREN and your clean energy provider may offer heat pump incentives; we verify them before quoting.
We repair furnaces in Monte Sereno as well as Los Gatos, Saratoga, Campbell, Cupertino and Santa Clara.
More services in Monte Sereno
- AC Repair in Monte Sereno
- Heating Repair in Monte Sereno
- Heat Pump Installation in Monte Sereno
- AC Installation in Monte Sereno