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Furnace Starting, Then Shutting Off? A Failing Pressure Switch in Henderson

A furnace pressure switch shuts the furnace down when it doesn’t sense proper draft from the inducer motor, so a failing switch often shows up as a furnace that starts, then quits. During a winter tune-up in this Henderson home, we found the switch intermittently failing, replaced it, and verified the inducer motor, venting, and burner flame.

Open Amana furnace showing internal components, wiring, and blue burner flames during a system diagnostic and pressure switch replacement

What We Found

  • During a winter tune-up, the pressure switch was failing intermittently. The inducer was pulling about -0.9 in. w.c. of draft, well past the -0.55 in. w.c. the switch needs to close, yet the switch still failed to close. That pointed to the switch itself.
  • We also checked the attic insulation and found it below optimal levels.

How We Fixed It

  • Replaced the pressure switch.
  • Checked the inducer motor, venting and burner flame: the inducer draws normal amps and spins freely, and the vent is clear.
  • The new part is covered by a 3-year warranty, and our labor by a 1-year warranty (2 years on Bob’s Family Plan).
Close-up of attic insulation with a measuring tape showing insulation depth, ensuring proper energy efficiency and heat retention for the home.
Technician using a digital multimeter to measure voltage and troubleshoot a pressure switch inside a furnace system
Open Amana furnace showing internal components, wiring, and blue burner flames during a system diagnostic and pressure switch replacement
Close-up of a furnace inducer motor with a visible barcode, verifying model and ensuring proper operation during a winter HVAC tune-up

How it turned out

The new pressure switch is in, and the inducer motor, venting and burner flame all checked out.

When to call: if your furnace starts and then shuts off after a short time, or does this several times before giving up, call a technician. The pressure switch is a safety device, so never bypass it. Attic problems can raise your bills too: see hidden attic problems and is your attic wasting money. Call (702) 381-5080 →

Questions homeowners ask

What does a furnace pressure switch do?It’s a safety switch. It confirms the inducer motor is pulling combustion gases out through the vent before the furnace is allowed to light. No draft, no flame.

Why does my furnace start, then shut off after a few seconds?If the pressure switch doesn’t confirm proper draft, the control board stops the startup. A failing switch, a blocked vent or a weak inducer motor can all cause it. A different cause of on-and-off heat: a corroded control board fuse.

Is it the switch or the inducer motor?A technician tests both: whether the inducer pulls proper draft, and whether the switch responds to it. On this job the inducer pulled -0.9 in. w.c., more than the -0.55 in. w.c. the switch needs, and the vent was clear, so the switch itself was at fault.

Expert insight

“Never bypass a pressure switch to get the heat back on. It’s the safety check that confirms exhaust gases are leaving your home. When a furnace starts and then shuts off, we test the switch, the inducer motor and the venting, and replace only what’s actually failing.”
Luis Perez, Install Manager at Bob's Repair
Luis PerezInstall Manager

Safety note: HVAC repairs involve high voltage, refrigerant and, on gas furnaces, combustion gases. Leave them to a licensed technician.

Team of Bob's Repair technicians in Paradise, NV, performing maintenance on outdoor AC units to extend their lifespan, set against the backdrop of a local home and a palm tree.

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