Why is my furnace blowing cold air? Here is the honest version: what you can safely check yourself in the next five minutes, what a technician usually finds when it is not that, and exactly what it costs to find out.
By Full Swing Plumbing Heating & Cooling, Greater Boston, MA. Updated September 27, 2026. Rated 4.9 out of 5 across 874 reviews.
If this means no heat in the house: A home with no heat is treated as urgent and prioritized, often same-day. The emergency button on the booking page gets a callback within 60 seconds.
If one of these fixes it, you owe us nothing and we are glad. If not, the next part is what the visit is for.
Flame sensor. If cleaning the sensor makes it run, that is not the repair. The board is usually the thing that has gone weak and is no longer sending the sensor enough voltage. And what kills the board is the same unfiltered air that packs the cabinet and rusts everything in it.
Igniter. The book pairs the igniter with the sensor and the burner on the same check: when the igniter is out the sensor and the pilot burner are cleaned with it, because the three light the furnace together and the burner door is open once. A new igniter lasts when nothing touches its surface and the air across the burners is clean; the book's handling rule is the whole prevention.
Pressure switch. The book's three reasons a pressure switch will not prove are all blockages, and on a condensing furnace the one that fills the switch tube is a backed-up drain. Clear the drain and the switch sees its draft again. The other two are the vent and the tube: a stopped vent or a plugged inducer port, and the chimney is checked on every call.
These are the causes in the manufacturers' troubleshooting charts and the trade handbooks our technicians train on, in plain words. The visit proves which one it is with a meter before anything is replaced.
The sensor itself is cleaned with a cloth, never sanded, because sanding it shortens the life of the part you just cleaned.
The igniter is proved with a meter before it is condemned, and gas pressure is set on every heating call.
$59 on weekdays, $159 evenings and weekends. Published and final, pre-tax, and the price is the price whether we find a loose wire or a bad motor.
Book the $59 visit online Or call (781) 424-0700Real arrival windows, including evenings and weekends. Paying is what confirms the slot; the office calls to confirm the window.