Quick answer
On a Goodman furnace, 3 flashes means the pressure switch is stuck open: the inducer fan is running, but the switch that proves draft has not closed, so the burners will not light. Clear snow and ice from the intake and exhaust pipes outside and check that the condensate drain is not frozen or kinked. Never jumper the switch. If the code continues, call a technician.
On a Goodman furnace, 3 flashes means the pressure switch is stuck open. The induced-draft blower, the small fan that starts first, is running, but the pressure switch circuit has not closed to prove that air is moving through the vent, so the board refuses to light the burners. You will hear the inducer run continuously with no ignition. Flash codes differ from one Goodman board to another, and where the legend on your furnace door disagrees with this page, go with the door.
Is it safe to keep running with 3 flashes showing?
The furnace is protecting you, and it will not light until the switch closes. A pressure switch exists to confirm that combustion gases have a clear path outdoors before any gas is released. Do not jumper or bypass it: a furnace firing into a blocked vent pushes exhaust, carbon monoxide included, back into the house. The inducer keeps running for as long as the thermostat calls for heat, so turn the thermostat down while you check outside.
The safe homeowner check: the pipes outside and the drain
In a Burlington or Hamilton winter, start outside. A high-efficiency Goodman breathes and exhausts through plastic pipes, and the terminations sit where drifting snow, ice from the exhaust's own moisture, or a nest built over the summer can choke them.
- Find the plastic intake and exhaust pipes where they leave the house and clear snow, ice and leaves from around and inside the openings by hand. Do not chip at the pipe itself.
- Follow the condensate tube from the furnace to the floor drain or pump. Straighten any kink, and if it passes through a cold space, check that it is not frozen.
- If there is a condensate pump, confirm it is plugged in and its tank is not full.
- Turn the thermostat back up and give the furnace a fresh start.
Two related guides go deeper on those checks: what to do when a furnace vent is blocked by snow and what to do when the condensate line is frozen.
What causes a Goodman pressure switch to stay open
- A blocked flue or inlet air pipe. Snow, ice or debris at either pipe cuts the airflow the switch is measuring.
- A blocked condensate drain system. Water that cannot drain backs up inside the furnace and changes the pressure the switch sees, which is why a drain problem shows up as a draft code.
- A blocked, pinched or disconnected pressure-switch hose. The small rubber tube that carries the pressure signal to the switch cracks with age, slips off its fitting or fills with water.
- A weak induced-draft blower. A tired motor spins too slowly to pull the switch closed, often with a new whine or rumble at startup.
- A faulty switch. It is last on the list for a reason: a switch that reads open is usually reporting a real problem.
The order matters because the cheap causes are also the likely ones. A furnace that showed 3 flashes on the morning after a snowfall, or on the first hard freeze of the season, usually has a pipe or drain problem and not a failed part. One that shows it in mild, dry weather deserves a closer look at the hose and the inducer.
What a technician tests on 3 flashes, and what the repair costs
With the pipes clear and 3 flashes still showing, the drain, the inducer and the switch need testing with a manometer. The technician connects the gauge to the switch hose, reads the actual draft with the inducer running, and compares it with the closing pressure printed on the switch. That one reading separates a failed switch from a furnace that is not producing enough draft. It is also why replacing the switch on a guess so often leaves the code in place.
- Diagnostic visit: $90–$150, applied to the repair when you proceed.
- Condensate drain cleaning or trap replacement: $150–$350.
- Pressure switch replacement: $250–$500.
- Draft inducer motor: $400–$900.
For a Goodman that still shows 3 flashes after the outdoor pipes are clear, book furnace repair with a TSSA-licensed technician. ZK Mechanical works from Burlington across Oakville, Milton, Hamilton and Mississauga; call (647) 801-1252 or send us the details. The Goodman furnace error code guide lists the other flash counts, and the pressure switch glossary entry explains the part.