TL;DR
A furnace pressure switch is the diaphragm safety device that proves the inducer fan is actually pulling combustion gases through the heat exchanger and flue before the control board allows ignition, closing its contacts only when it senses the proper negative pressure through a small rubber hose. A switch that will not close — from a blocked flue, cracked hose, or plugged condensate port on high-efficiency units — is among the most frequent furnace lockout causes.
What it means
A furnace pressure switch is the diaphragm safety device that proves the inducer fan is actually pulling combustion gases through the heat exchanger and flue before the control board allows ignition, closing its contacts only when it senses the proper negative pressure through a small rubber hose. A switch that will not close — from a blocked flue, cracked hose, or plugged condensate port on high-efficiency units — is among the most frequent furnace lockout causes. Jumpering it defeats the safety and is diagnostic only, never a fix.
Where it sits in the glossary
Furnace pressure switch is part of the Trade jargon group inside the ProFix Directory glossary. Browse every term in this category from the glossary index.
Why Ohio homeowners should know it
This is a term Ohio homeowners encounter when reading contractor quotes, hiring paperwork, or inspection reports. Understanding it well enough to ask one good follow-up question is usually all the protection a homeowner needs.
ProFix Directory keeps definitions short on the index page and saves the longer context — Ohio-specific rules, where the term comes from, and which ProFix tools touch it — for these per-term pages so the term is easy to cite and easy to share.
ProFix tools that touch this term
See also
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