A furnace tune-up in Menlo Park, Atherton or Portola Valley is mostly about the first cold night. With mild winters, many furnaces run only a few months a year and sit idle the rest: dust settles on the burners, flame sensors pick up a coating, condensate traps dry out or clog. A fall visit cleans what affects safety and airflow, takes the measurements that show how the furnace is really running, and finds worn parts while there is still time to replace them on your schedule instead of at 10 PM in December.
When to book
September through early November, before the first nights in the 40s. Portola Valley’s foothill nights run cooler than the bay side, so furnaces there tend to start earlier and run longer; book early. If the furnace shares its blower with central air, or you have a heat pump, a spring AC tune-up covers the other season.
What the tune-up covers
| Task | What we look for |
|---|---|
| Heat exchanger inspection | Cracks, rust-through or heat stress that could let combustion gases into the air |
| Burner cleaning and adjustment | A steady, even flame; dust and rust removed; clean light-off |
| Flame sensor | Cleaned, and a signal strong enough to prove the flame every time |
| Safety controls testing | Limit, rollout and pressure switches and the door switch, each made to trip |
| Flue inspection | Tight joints, correct slope, no rust holes or blockage, proper draft |
| Carbon monoxide check | CO in the flue gas and in the air around the furnace |
| Filter replacement | The right size, seated with the airflow arrow the right way |
| Blower and electrical | Blower wheel, motor amp draw, capacitor, wiring and the furnace circuit |
| Condensate (90%+ furnaces) | Trap cleaned, drain flowing, no leaks at the plastic vent pipes |
Older furnaces with a standing pilot also get the pilot assembly and thermocouple checked. If your system uses a thick media filter, tell us the size when you book.
Measurements, not a wipe-down
What separates a real tune-up from a quick look is the numbers. Every furnace label lists a temperature-rise range: the difference between the air going in and the air coming out while the burners run. A rise above the range usually means poor airflow from a clogged filter, closed registers or leaky or crushed ducts, and it makes the furnace run hot. A rise below the range can point to low gas pressure. We also check gas pressure at the valve, the flame-sensor signal, the blower’s amp draw and the static pressure in the ducts. Keep the readings with your records, so next year’s visit can be compared with this one.
Checks that depend on where the furnace sits
- Attic furnaces: the drain pan and condensate line, insulation kept off the cabinet and the vent, a safe path to the unit, and signs of rodents around the return.
- Hall closets: combustion-air openings clear, nothing stored against the furnace, a return grille that is not choked by a door or furniture.
- Garages: no paint, solvents or gasoline near the furnace, the cabinet protected from car bumpers, and no return air drawn from the garage.
What a tune-up does not include
A tune-up is a fixed-scope visit. It does not include repairs, replacement parts other than the filter, or duct cleaning. If the visit finds a weak capacitor, a cracked igniter or a noisy inducer, you get the finding and a price before anything is replaced, and you decide. If the heat exchanger is cracked or carbon monoxide shows up, the furnace stays off and the technician shows you why; furnace repair explains what comes next. Dust from the registers or a musty smell is a separate question, for indoor air quality or duct cleaning.
The first-cold-night smell
The first run after summer often smells of burning dust for a few minutes while the heat exchanger burns it off. That fades. A smell that stays, smells like gas, or smells like hot plastic or wiring means turn the furnace off and call.
Between visits
- Change the filter every one to three months while the heat is on, and more often with pets or during smoke days from wildfires.
- Keep supply registers and return grilles open and clear of rugs and furniture.
- Test smoke and carbon monoxide alarms, and replace them when they reach the end of their rated life.
- Keep the furnace closet or corner clear of storage.
One visit or a plan
A single tune-up suits a furnace that gets checked every fall anyway. With a furnace and an air conditioner, or a heat pump that works year-round, an HVAC maintenance plan covers both seasons. Before buying any plan, confirm the exact tasks and measurements, what is excluded, how repair discounts and priority scheduling work, and the renewal and cancellation terms.