Furnace Pressure Switch Stuck Open — What It Means & Fix (Greater Vancouver)

If your furnace is reporting a “pressure switch stuck open” fault — whether you read it as a blink code, on a control board, or on a modern communicating thermostat — here is what it is telling you in plain terms: the furnace cannot confirm that it is venting safely, so it is refusing to light the burners. That is not the furnace being fussy; the pressure switch is a critical safety that proves the exhaust is actually leaving the house before any gas is burned. A “stuck open” message means that proof never arrived. For a Greater Vancouver homeowner, this is one of the most common no-heat faults we see, and it is often tied to our wet climate.

This is a cross-brand explanation, because the pressure switch works on the same principle on virtually every modern gas furnace — Lennox, Carrier, Goodman, Rheem, Trane, Bryant, Daikin, Tempstar and the rest. The inducer motor starts, it should create enough draft to pull the pressure switch closed, and only then does the control proceed to ignition. If the switch stays open, the sequence stops. Your brand’s exact code for this is on the legend inside the blower-compartment door, but the meaning is universal.

ROMA Heating & Cooling has diagnosed pressure-switch faults on furnaces of every brand across Vancouver, Burnaby, Richmond, Surrey and the North Shore since 1999. Here is what “stuck open” means, the common causes, the safe checks, and when to call a technician.

What “pressure switch stuck open” means

Start with how the safety works:

• The inducer must prove draft: when the inducer runs, it should create enough negative pressure to snap the switch closed.
• “Stuck open” means no proof: the control expected the switch to close and it did not, so it halts before ignition.
• It is protecting you: a switch that will not close often means the exhaust is not leaving properly — exactly when you do not want to burn gas.

Importantly, “stuck open” is more often about a venting or condensate problem the switch is correctly sensing than about the switch itself being broken. The switch is usually the messenger.

The common causes of a stuck-open pressure switch

📞 Talk to a licensed ROMA furnace technician — (604) 704-0300

Blocked intake or exhaust vent

On high-efficiency furnaces, the sidewall vent terminals can clog with leaves, snow, ice, or a nest, so the inducer cannot establish draft. Safe check: inspect and clear the outdoor intake and exhaust terminals.

Full or blocked condensate trap and line

A high-efficiency furnace drains acidic condensate; if the trap or line clogs, water backs up and holds the switch open. Safe check: check for water backing up and clear the condensate trap and drain line if you can do so safely.

Disconnected or cracked hose

The small rubber tube between the switch and the inducer can slip off, crack, or fill with condensate. Safe check: none internal — a technician inspects and clears or replaces the hose.

Weak or failing inducer motor

An inducer that spins slowly cannot create enough draft to close the switch. Safe check: none internal — a technician tests the inducer.

Failed pressure switch

Occasionally the switch itself has failed and will not close under correct draft. Safe check: none — a technician measures the draft and the switch together.

Stuck-open quick reference

Safe things to try once

Because this fault is so often a venting or condensate restriction, there are useful homeowner checks. Go outside and inspect the furnace’s intake and exhaust terminals — usually a pair of plastic pipes on an exterior wall — and clear away leaves, snow, ice, or any nest blocking them. Check around the base of the furnace for water, which suggests a backed-up condensate trap or line you may be able to clear. Replace a dirty 1-inch filter and make sure the blower door is fully seated. Then cycle power once and watch a start attempt. If the inducer runs and the furnace now lights and stays lit, a cleared vent or drain solved it. If the “stuck open” fault returns, stop — the hose, inducer, and switch are internal components a licensed gas technician tests, and you should never bypass or jump the pressure switch to force ignition. That safety exists to keep exhaust out of your home.

How ROMA fixes a stuck-open pressure switch

We diagnose the whole venting path, not just the switch, because the switch is usually reporting a real condition. We start the furnace and measure the actual draft the inducer produces, then confirm whether the switch closes as it should at that draft. We inspect the intake and exhaust for restrictions — a frequent find in our wet, leafy climate — and check the condensate trap and line for blockage and backup. We examine the pressure-switch hose for cracks, disconnection, or trapped condensate, and we test the inducer motor. Only if the venting, condensate, hose, and inducer all check out and the switch still will not close under correct draft do we replace the switch itself. We confirm the fix by watching the furnace prove venting and complete a full heat cycle before we leave. When you call (604) 704-0300, tell us whether the fault started after a storm and whether you see water near the furnace — that points us straight at the cause.

When it is an emergency

A pressure-switch fault is usually not an emergency — the furnace is protecting you by not lighting — but the gas and CO rules always apply. If you smell gas, leave the home and call the FortisBC emergency line and 911 from outside; do not troubleshoot. If a CO alarm sounds or anyone feels unwell, get everyone out and call 911. Never bypass the pressure switch to keep the furnace running, because doing so removes the very safety that confirms your exhaust is leaving the house. If you are without heat in a genuine cold snap, call us for priority scheduling.

Repair or replace?

Almost every cause of this fault is an inexpensive, common repair on an otherwise sound furnace — clearing a vent or condensate line, replacing a cracked hose, or fitting a new pressure switch. A failing inducer motor is a moderate repair that still makes sense on a newer furnace. Replacement of the furnace only enters the conversation on an older unit with stacking issues, where we compare the repair against a high-efficiency upgrade with any available rebates. We quote the repair first, after diagnosis.

Greater Vancouver context

This is a signature wet-climate fault. High-efficiency condensing furnaces are common across Metro Vancouver, and their sidewall vent terminals sit exposed to our rain, wind-blown leaves, and occasional snow, while their condensate traps run constantly in cool Burnaby, New Westminster and North Shore mechanical rooms. A storm that blocks a terminal, or a slow drain that finally backs up, will produce a “pressure switch stuck open” fault overnight. Keeping the vent terminals clear and the condensate drain flowing prevents most of these no-heat calls, which is exactly what an annual tune-up checks.

What to note before you call

Because this fault is usually the switch correctly sensing a venting or condensate problem, a few observations point us straight to the cause. Note whether the fault started after a storm, heavy rain, or snow, which suggests a blocked vent terminal, and whether you see water pooling near the base of the furnace, which suggests a backed-up condensate trap or line. Mention whether the inducer motor spins up when the furnace tries to start, since an inducer that runs but cannot close the switch narrows things to the hose, the venting, or the switch itself. With the brand and model from the cabinet, we can reference the correct code legend and arrive ready to measure the actual draft rather than guessing at the part.

Why ROMA for pressure-switch faults in Vancouver

ROMA Heating & Cooling is a TSBC-licensed gas contractor (Gas licence LGA0202903), bonded, insured and Red Seal-trained, rated 4.8★ from 221 Google reviews. Whatever brand you own, we measure the draft, trace the venting and condensate path, and fix the true cause of a stuck-open pressure switch — never bypassing the safety — with upfront flat-rate pricing and no hidden fees. Estimates on installs are free, 0% financing is available OAC, and we work seven days a week. See our furnace repair service or book a free estimate. We serve Vancouver, Burnaby, Richmond, Surrey, Coquitlam and the North Shore — call (604) 704-0300, reach our team, or ask about maintenance plans that keep vents and drains clear.

Frequently Asked Questions

What does 'pressure switch stuck open' mean on a furnace?

It means the control never saw the pressure switch close when the inducer ran, so the furnace cannot prove it is venting safely and will not light the burners. It is usually caused by a blocked vent, a full condensate trap, a disconnected hose, or a weak inducer — not always a bad switch. Call ROMA at (604) 704-0300 if it stays.

Can I fix a stuck-open pressure switch myself?

You can safely clear the likely causes: check and clear the outdoor intake and exhaust terminals, clear a backed-up condensate trap and drain, and replace a dirty filter. If the fault returns after that, stop — the hose, inducer, and switch are technician items. Never bypass or jump the pressure switch; it is a safety.

Why does my furnace get this fault in wet or snowy weather?

High-efficiency furnaces vent through sidewall terminals that rain, leaves, and snow can block, and condensate traps that can back up in cool weather. Either one keeps the inducer from establishing the draft needed to close the pressure switch, producing a stuck-open fault. It is a common Greater Vancouver wet-climate call.

Is it dangerous to run a furnace with a pressure-switch fault?

The furnace protects you by refusing to light, so leaving it faulted is safe. The danger comes from bypassing the switch to force it to run, which removes the safety that confirms exhaust is leaving your home and risks combustion gases indoors. Never jump a pressure switch — have the cause repaired.

Does ROMA repair furnace pressure-switch faults in Greater Vancouver?

Yes. ROMA Heating & Cooling measures the draft and traces the venting and condensate path on any brand to fix the true cause across Vancouver, Burnaby, Richmond, Surrey and the North Shore. We are TSBC-licensed, bonded and insured. Call (604) 704-0300 seven days a week.

Reviewed by the ROMA Heating & Cooling team — TSBC-licensed gas contractor (Gas LGA0202903), serving Greater Vancouver since 1999. Updated July 2026.

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