System Components
Pressure Switch
A safety device in your furnace that verifies the exhaust vent is clear and the draft inducer motor is running before allowing the gas valve to open.
What Is a Pressure Switch?
The pressure switch is a critical safety device that ensures proper venting before your furnace ignites. When the draft inducer motor starts, it creates negative pressure in the heat exchanger and flue. The pressure switch detects this negative pressure and signals the control board that it's safe to proceed with ignition. If the switch doesn't close (due to a blocked vent, failed inducer motor, cracked pressure hose, or the switch itself failing), the furnace locks out and won't light.
Why It Matters for Your Home
A pressure switch lockout is your furnace protecting you from a potentially dangerous situation — it means something is preventing proper exhaust venting. While the switch itself sometimes fails, the problem is often elsewhere: a blocked flue, bird's nest in the exhaust pipe, failed draft inducer motor, or condensate backup. A thorough technician will diagnose the root cause, not just replace the switch.
Furnace locked out? Call Trademark Tek at 541-500-0663 for expert diagnosis that finds the real problem.
Quick Facts
Category
System Components
Also Known As
Pressure Switch
