Furnace Repair in Novato

Four things worth checking before you call

Four checks resolve a meaningful share of no-heat calls and cost nothing. Thermostat batteries, since a blank screen and a cold house look exactly like a dead furnace. The service switch on or beside the cabinet, which looks like a light switch and gets flipped by anyone storing boxes in the closet. The filter, because a restricted return makes the heat exchanger run hotter than design and the high-limit switch then cuts the burners to protect it. And the blower door, which has an interlock that kills power when the panel is not seated, catching people after a DIY filter change.

If none of those is it, describe the symptom precisely when you book. "It runs then shuts off after two minutes" and "it never lights at all" point at different halves of the machine, and the difference lets us load the right parts before leaving Petaluma. If a carbon monoxide alarm has sounded, get everyone outside and call from there.

What fails

Furnaces fail in a small number of ways, and the distribution is not random.

Flame sensor. A thin rod in the flame path develops an oxide film that blocks the sensing current. The furnace lights, the board fails to see flame, the gas valve closes, and it retries and locks out. This is a wear item and among the least expensive real repairs there is. It is also the fault most often misdiagnosed as a dead gas valve.

Hot surface igniter. Silicon carbide and silicon nitride igniters crack from thermal cycling. The inducer runs, nothing glows, and no ignition attempt happens.

Pressure switch not closing. Sometimes the switch, more often what it senses. On a condensing furnace, a plugged condensate trap backs water into the system and holds the switch open. A cracked hose, a failing inducer wheel, or a restricted flue does the same.

High-limit trips. Almost always airflow: filthy filter, undersized or blocked returns, crushed flexible duct, too many closed registers. Worth taking seriously, since years of overheating cycles are one mechanism that fatigues a heat exchanger into cracking.

Rollout switch. A trip here means flame came out of the burner box where it should not, pointing at a blocked exchanger or venting problem. It is never a switch to simply reset.

Blower. Older units use a permanent split capacitor motor, and the capacitor is a common inexpensive failure. Variable-speed ECM motors fail at the control module more often than at the motor, and that module is model-specific.

Control board. Boards fail outright and boards fail intermittently. The intermittent ones are why a technician who spends half an hour watching a unit run finds things a ten-minute visit does not.

How we decide between repair and replacement

We walk the diagnosis through four checks in order. The first one that fails ends the discussion, which keeps the decision from turning into a sales pitch.

Safety. Heat exchanger integrity and combustion. If that fails, the unit is done, and no component repair reopens it.

Age against the horizon. The furnace's remaining service life measured against the 2029 zero-NOx compliance date on the district's furnace rule. Repairing a unit with real life left is straightforward. Putting a major assembly into one that will need replacing inside the same window is harder to justify.

The part. Wear item, major assembly, or a discontinued board that has to be sourced. Availability matters as much as the component, because manufacturers stop making boards and blower assemblies for older model lines.

The house. What else is on the same clock. If the air conditioning is the same vintage and still running R-22, that shifts the picture, since R-22 production and import ended in the United States in 2020 and repairs now draw on reclaimed or stockpiled refrigerant. Whether the ducts can carry the airflow the equipment needs counts too. So does whether you were already planning to electrify, because a heat pump in a Novato home replaces the furnace and the air conditioner in one move.

Note what that last check does not say. An existing R-410A air conditioner does not need replacing, because the AIM Act phasedown's 700 GWP limit applies to newly manufactured residential and light commercial equipment. That transition affects what we install next, not what you already own. If cooling is the weak link, air conditioning repair in Novato is often handled on its own.

What drives the cost

We give you the price before work starts, and it helps to know what moves it, since one symptom can land in very different places. The class of the failed part is the largest factor, with wear items at one end and sealed assemblies and model-specific electronics at the other. Parts availability on a discontinued model can matter more than the component itself. Access is real labor: a garage furnace with three feet of clearance and one wedged into a hallway closet beside the water heater are not the same job. Cascading damage adds scope, because a shorted board can take the transformer with it. Where the failure exposed a duct or return problem, correcting the airflow is what stops the new part from dying the same way. On the replacement path, venting, gas line sizing, condensate routing, permit, and inspection all become part of the work.

What we will not do is quote a repair over the phone from a symptom. A furnace that shuts down after two minutes has at least six plausible causes.

On the replacement path, sizing and incentives come before equipment

If the answer is replacement, the load calculation happens before anyone talks about brands.

The default failure in this trade is oversizing. A contractor reads the nameplate on the old furnace, matches the input rating, and moves on, which perpetuates whatever was wrong the first time. In Novato that is usually too much capacity, because equipment sized decades ago was sized generously and houses have since been re-roofed, re-windowed, or insulated. An oversized furnace satisfies the thermostat fast, short-cycles, leaves rooms uneven, and burns through ignition components early.

A load calculation looks at the building: square footage, orientation, window area and glazing, insulation, duct location and leakage, infiltration. Mid-century houses and newer subdivisions in the same zip code routinely calculate out at different loads. We size to that result, then confirm the existing ducts can carry the required airflow.

On the electric path the panel enters the conversation. A heat pump with auxiliary electric heat draws meaningfully more than a gas furnace, so panel capacity and an electrical load calculation belong in the same discussion. That is why an electrical panel upgrade in Novato sometimes appears inside an HVAC quote.

Incentives follow the same split, and the split is worth stating plainly: the money is on the electric path. Nothing rebates a gas furnace replaced by another gas furnace.

• MCE is the community choice energy provider for Novato and offers residential heat pump rebates covering heat pump space heating and cooling, with a separate rebate for heat pump water heaters.
• Income-qualified households have a stronger set of options, and it is worth asking rather than assuming. MCE's programs for qualifying homes cover energy upgrades directly, and the eligibility line is drawn by household income rather than by the equipment.
• MCE's heat pump rebates are the main local option, and only on the electric route. Twelve months of ownership and residency in a single-family detached home, a participating contractor who files the paperwork, and an application made before installation rather than after.

California's Building Energy Efficiency Standards also attach requirements to replacement work, and the 2025 edition took effect January 1, 2026 per the California Energy Commission. Which measures apply to your changeout is confirmed with the building department at permit time, not assumed from a new-construction rule.

Install day in a Novato utility closet

Replacement day is where the housing stock stops being a talking point and becomes the job.

Combustion air. A gas appliance in a confined closet needs a defined volume of combustion air, usually through upper and lower openings. Closets get modified over the years: shelving added, vents blocked, a louvered door swapped for a solid one.

Venting, and the water heater beside it. Many Novato closets have the furnace and water heater sharing one vent. Replacing an older furnace with a high-efficiency condensing model takes it off that flue entirely, since condensing units vent through plastic pipe out a sidewall. The water heater is then alone on a vent sized for two appliances, which can draft poorly and condense inside the flue. The consequence is well understood and so are the fixes, but it has to be handled as part of the furnace job rather than discovered afterward. When the water heater is also near end of life, planning both together is the cleaner path, which is where water heater work in Novato enters the conversation.

Condensate. A condensing furnace produces acidic condensate needing a proper drain path, a trap, and sometimes a pump. Closet and attic locations have to route it somewhere that will not damage the house.

Gas and electrical. Input ratings change between old and new equipment, so gas line capacity is verified rather than assumed, and the furnace circuit and low-voltage control wiring get checked at the same time.

Duct connections. The plenum transition is where installers cut corners, and a new furnace tied into an old plenum with sloppy transitions gives back much of the efficiency you paid for.

Inspection, and what gets checked

The building inspector looks at what hurts people: venting and clearances, combustion air, gas piping and connections, the electrical disconnect and bonding, condensate routing, and whether the installation matches the permit. We commission the unit before the inspector arrives, verifying that temperature rise falls within the manufacturer's stated range, confirming gas pressure, taking static pressure, and running a full cycle. A furnace operating outside its designed temperature rise is either starving for air or overfiring, and both shorten its life.

The follow-up, and the interval that prevents the next call

Most repeat furnace failures are airflow failures with a delay. Filters get changed on a schedule through the heating season, at an interval set by the filter and the household rather than the calendar month. Annual service before the first cold stretch is what catches drift: a flame sensor beginning to foul, a capacitor reading low, a condensate trap loading up, a sensing hose gone brittle. Those are the parts that quit on the coldest night, and none of them quit without warning if someone is measuring. Our maintenance program exists for that.

One more item worth planning for. Hillside areas of Novato face fire risk and PG&E Public Safety Power Shutoffs, and a gas furnace is not independent of the grid. Control board, inducer, and blower all run on electricity, so the heat stops when the power does. If that matters at your address, it is a backup power conversation, and we are a Certified Generac Generator installer. Designing it in during an HVAC project costs far less than retrofitting it later.

The Novato addresses we work in

We work throughout Novato: Hamilton, Bel Marin Keys, Indian Valley, downtown, and the hillside neighborhoods, plus addresses outside the city limits that permit through the county. What changes from one to the next is rarely the neighborhood name and almost always the house, since construction era determines where the equipment sits, how it vents, and how the ducts were run. Furnace work is one part of our Novato heating and cooling service.

How to choose a contractor for furnace work in Novato

Four questions separate a real quote from a guess. Ask whether the heat exchanger was inspected and how, because a vague answer means the safety check was never done. Ask for the load calculation behind any replacement proposal, since a contractor who sized from the old nameplate will not have one and will usually explain that the calculation is unnecessary. Ask who pulls the permit and which agency issues it. Ask what happens to the water heater if the new furnace vents differently, because anyone who has not considered the shared flue has not looked closely at your closet.

Ongaro & Sons is Diamond Certified, a Trane Comfort Specialist and Mitsubishi Diamond Contractor Elite, and holds a BBB A+ Rating.

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