Furnace Pressure Switch Explained: Symptoms, Failure Causes, and When It Needs Replacement

When your furnace suddenly stops working—especially during a cold Winnipeg winter—the issue is often linked to a furnace pressure switch. This small but critical safety component protects your home from dangerous exhaust gas problems and prevents the furnace from operating when conditions are unsafe.

Understanding how the pressure switch works, the warning signs of failure, and when replacement is necessary can save you from unexpected breakdowns, costly repairs, and uncomfortable nights without heat.

What Is a Furnace Pressure Switch?

A furnace pressure switch is a safety device designed to confirm that your furnace can safely vent combustion gases—such as carbon monoxide—out of your home before ignition begins.

It works alongside the draft inducer motor, which pulls exhaust gases through the heat exchanger and out the vent pipe. The pressure switch monitors air pressure through small rubber tubes. If proper airflow is not detected, the switch remains open, and the furnace will not ignite.

This prevents: - Backdrafting of exhaust gases - Carbon monoxide buildup - Damage to furnace components

The pressure switch is typically a round plastic or metal component located near the inducer motor and connected by small hoses and electrical terminals.

What Does a Furnace Pressure Switch Do?

Safety Comes First

The pressure switch confirms that combustion byproducts can be safely exhausted outside before the burners turn on.

Monitors Proper Airflow

It senses the negative air pressure created by the inducer motor pulling air through the furnace system.

Controls the Ignition Sequence

If airflow is insufficient, the pressure switch stops the ignition process immediately—often triggering a safety lockout.

Common Symptoms of a Bad Furnace Pressure Switch

If your furnace pressure switch is failing, you may notice one or more of these signs:

Furnace Won’t Produce Heat

The furnace attempts to start, blows cool air briefly, then shuts down.

Error or Lockout Codes

Many modern furnaces display flashing LED codes indicating a pressure switch fault.

Short Cycling

Your furnace turns on and off repeatedly without completing a full heating cycle.

Inducer Motor Runs, But Furnace Won’t Ignite

You may hear the inducer motor start, but the burners never light.

These symptoms are common during Winnipeg’s cold months when furnaces are working hardest.

Common Causes of Pressure Switch Problems

In many cases, the pressure switch itself isn’t the real problem. Instead, it’s reacting correctly to unsafe conditions.

Blocked Exhaust Vent

Ice, snow, leaves, or debris can block vent pipes—very common during Winnipeg winters.

Dirty or Clogged Air Filter

Restricted airflow prevents proper pressure from forming.

Clogged Condensate Line or Trap

High-efficiency furnaces produce condensation that must drain properly.

Faulty Inducer Motor

If the inducer motor can’t create enough airflow, the pressure switch won’t close.

Failed Pressure Switch

Over time, the internal diaphragm or spring can wear out and stop responding accurately.

When Should a Furnace Pressure Switch Be Replaced?

A furnace pressure switch should be replaced when:

• It fails electrical continuity testing
• It remains open even when airflow is confirmed
• The furnace repeatedly locks out despite clear vents and clean filters
• A licensed technician confirms internal failure

⚠️ Important: Bypassing or jumping a pressure switch is extremely dangerous and should never be done. This device exists to protect your home and family.

Basic Troubleshooting (Homeowner-Safe Checks Only)

Always turn off furnace power before inspecting anything.

You can safely check: - Exhaust and intake vents for snow or debris - Air filter condition (replace if dirty) - Condensate drain lines for visible blockages - Whether the inducer motor is running

If the issue continues, professional testing with a multimeter is required to diagnose the pressure switch correctly.

Why Pressure Switch Issues Are Common in Winnipeg

Winnipeg’s extreme cold, heavy snowfall, and long heating seasons make furnaces more vulnerable to: - Frozen vent pipes - Condensate line blockages - High system strain during peak winter demand

Regular furnace maintenance greatly reduces the risk of pressure switch failures during the coldest nights.

Professional Furnace Repair & Pressure Switch Service in Winnipeg

At LIDOMA Home Services, we specialize in: - Furnace diagnostics and safety inspections - Pressure switch testing and replacement - Furnace tune-ups and emergency repairs - Reliable HVAC service across Winnipeg

If your furnace is short cycling, showing error codes, or not producing heat, don’t wait for a complete breakdown.

Need immediate furnace repair in Winnipeg?
If your furnace isn’t starting or is showing a pressure switch error, our licensed technicians can help.
📞 Call us now: +1 204 297 4420
🔧 Service page: Furnace Tune-Up & Repair in Winnipeg Serving Winnipeg homeowners with trusted HVAC expertise.