What does a furnace pressure switch do? A furnace pressure switch proves the draft inducer is pulling exhaust out through the vent before the burners may light. Too little suction and it stays open, so the board will not ignite. If it is closed before the inducer starts, the board will not start either.
Key Takeaways
- Goodman defines the switch as a safety device that blocks combustion through a restricted or blocked vent (Goodman RS6612022).
- Setpoints are suction in inches of water column: one Goodman GM9S92 inducer switch opens at 1.20, its coil cover switch at 0.10 (Goodman trip point chart).
- The Resideo S9200U1000 board waits 150 seconds for the switch to close, then idles five minutes and retries (Resideo 69-2075).
- The White-Rodgers 50M56D-751 board flashes code 31 for “did not close” and 23 for “did not open” (White-Rodgers).
- Rheem lists six reasons a switch will not close; only one is the switch’s hose, and none is the switch itself (Rheem 801T manual).
- Rheem and Goodman forbid jumpering it; Rheem requires 15 minutes of testing on a new safety switch (Rheem).
What does a furnace pressure switch do?
A furnace pressure switch is a diaphragm switch, fed by a hose from the inducer or collector box, that closes only when the draft inducer creates enough suction. Goodman calls it “a safety device to prevent the combustion cycle from occurring with inadequate venting caused by a restricted or blocked vent pipe” (Goodman RS6612022).
The control checks it twice. A Goodman board confirms the switch is open, 0 VAC, before starting the inducer, and begins prepurge once it reads closed, 24 VAC. Our guides to where the ignition sequence stops and the flame sensor cover later steps.
Any furnace with an inducer has one: DOE describes mid-efficiency furnaces, 80% to 83% AFUE, as fan-driven, and condensing furnaces at 90% to 98.5% AFUE (DOE Energy Saver, archived copy). CPSC credits a voluntary furnace standard that “added blocked-vent shut-off devices” (CPSC release 02-255).
Where is the furnace pressure switch located, and what does the hose do?
The furnace pressure switch sits beside the inducer motor behind the burner compartment door, hosed to a port on the inducer or collector box. Goodman’s test starts: “Remove burner compartment door to gain access to pressure switch(es)” (Goodman RS6612022).
Goodman’s 90% furnaces carry two switches, on the coil cover and the inducer, each with its own setpoint. If the hose is cracked, kinked, loose or holding water, the switch never sees the real suction; on 90% models Goodman says to check it “for kinks and/or moisure” (sic).
What pressure closes a furnace pressure switch?
There is no universal number. Each furnace pressure switch is rated for its model in inches of water column (in. w.c.) of suction, printed on the switch. Goodman publishes a “set point on pressure fall,” where the switch opens as suction weakens, and a “max make on pressure rise,” the suction by which it must close.
| Goodman model (RS6612022 chart) | Coil cover switch opens at | Inducer switch opens at | Inducer switch must close by |
|---|---|---|---|
| GM9S92, *M9S920603BNAA | 0.10 ± 0.05 in. w.c. | 1.20 ± 0.05 in. w.c. | 1.41 in. w.c. |
| GM9S96, *M9S960603BNAA | 0.10 ± 0.05 in. w.c. | 1.49 ± 0.07 in. w.c. | 1.70 in. w.c. |
| GM9S96, *M9S961205DNAA | 0.10 ± 0.05 in. w.c. | 0.85 ± 0.05 in. w.c. | 1.00 in. w.c. |
| GC9S96, *C9S960403BNAA | 0.08 ± 0.04 in. w.c. | 1.49 ± 0.07 in. w.c. | 1.70 in. w.c. |
All values are suction readings from Goodman’s trip point chart. Two GM9S96 models differ by 0.64 in. w.c. at the inducer switch, so a “universal” switch is no basis for a repair. The 0.5 to 3.0 in. w.c. range on page one of Google traces to no manufacturer document we found.
Why is my furnace pressure switch stuck open?
A furnace pressure switch stuck open usually means the switch is telling the truth: there is not enough suction at the hose, so the board will not light. Rheem lists six reasons a switch will not close (Rheem 801T):
- An inoperative induced draft blower.
- A loose or leaky pressure switch hose.
- A blockage in the exhaust vent.
- Severe downdrafts canceling the inducer’s draft.
- A leaky gasket at the induced draft blower.
- An improperly sized or installed vent.
For the “open with inducer on” case, Goodman says an inducer that “runs continuously with no furnace operation” points to a blocked flue or inlet pipe, a “blocked drain system,” a weak inducer, a pinched hose or a bad switch (Goodman RS6612022). It also flags condensate in the inducer and a plugged switch port; see our condensate pump guide. Outdoors, CPSC warns that “birds, other animals and insects sometimes nest in vents” (CPSC).
The Resideo S9200U1000 waits 150 seconds, shuts the inducer off, idles five minutes and retries, and “this process continues indefinitely” (Resideo 69-2075). A switch that closes but drops out mid-cycle is one cause of a furnace that short cycles.
What does a pressure switch stuck closed mean?
A pressure switch stuck closed reads closed before the inducer starts, so the board treats it as a failed safety and will not start. Rheem: “the pressure switch contacts must open before the unit can go through another heating cycle” (Rheem 801T).
Goodman flashes E1 for a circuit “closed at the start of heating cycle” and lists two causes: sticking contacts, so replace the switch, or a short in the switch wiring (Goodman RS6612022). White-Rodgers’ 50M56D-751 board for Carrier furnaces calls it code 23, “Pressure Switch Did Not Open” (White-Rodgers). Resideo’s board flags it after five seconds and resumes once the switch opens (Resideo). That differs from a tripped high limit switch, which opens on heat.
How does the inducer motor work with the pressure switch?
The inducer motor creates the suction the pressure switch measures, so a dead, weak or obstructed inducer looks exactly like a bad switch. Goodman’s flowchart asks whether the inducer runs, then whether it has 115 volts (Goodman RS6612022).
No voltage points to the board or wiring; voltage with no rotation means “the inducer is defective or off on thermal protector,”: “If you have 115V and the motor does not run, replace the induced draft motor.” A running inducer can still fall short through a leaky gasket or condensate in the housing.
Goodman runs a 15 second post purge; if the switch drops out during prepurge, Resideo holds the inducer on up to 60 seconds to re-close it (Resideo). Only then does the board power the hot surface igniter.
What can a homeowner check, and what needs a technician?
A homeowner can read the fault code, cut power and look for visible blockages; opening the burner compartment, vent or drain is technician work, and Goodman marks drain service “QUALIFIED SERVICER ONLY” (Goodman RS6612022).
Safe owner checks:
- Count and note the flash code through the sight glass.
- Set the thermostat to off, then switch off the furnace’s service switch.
- Outdoors, clear snow, ice, leaves or nests from the intake and exhaust pipe ends you can reach.
- Look at any visible switch hose for a kink, loose end or water, without removing panels.
- Restore power once; if the code returns, call a technician.
| Check | Who | What it proves |
|---|---|---|
| Flash code count | Owner | Stuck closed or stuck open |
| Vent and intake terminations | Owner | Visible blockage |
| Manometer on the hose, inducer running | Technician | Suction versus the switch rating |
| Ohmmeter across switch contacts | Technician | Bad switch or weak suction |
| 115 V at inducer, winding test | Technician | Inducer motor or board fault |
| Drain trap, vent length and elbows | Technician | Water or vent restriction |
Goodman’s core test: with the inducer running, check the contacts with an ohmmeter; if open, “compare the negative reading on the manometer with the rating on the pressure switch.” A blocked vent is also a carbon monoxide risk; CPSC urged yearly inspections “checking chimneys, flues and vents for leakage and blockage” (CPSC), and our guide to CO alarm placement covers the backup.
Can you bypass a furnace pressure switch, and when is replacement right?
No. Jumpering a furnace pressure switch lets burners fire with no proof exhaust is leaving, and every manufacturer document we read forbids it. Rheem: “DO NOT BYPASS, JUMPER, OR REMOVE ANY SAFETY SWITCH FROM THE FURNACE CONTROL CIRCUIT” (Rheem 801T). Goodman: “Never by-pass or alter furnace controls” (Goodman).
Correction: a top-ranking page tells readers to jumper the switch wires as a diagnostic step. Rheem calls a safety switch shutdown “an indication of a potential safety hazard.”
Replace the switch only when the manometer shows suction above its rating with contacts open, or contacts stick closed. Rheem requires “identical OEM replacement parts” and a test of at least 15 minutes on any new safety switch. Goodman assigns switch assemblies by model: 0130F00480 for the GM9S92 above. No federal price series covers it, as our furnace repair cost breakdown explains.
Condensing, two-switch furnaces are coming: the federal minimum for non-weatherized gas furnaces rises from 80.0% AFUE to 95.0% for units made on and after December 18, 2028 (10 CFR 430.32(e)), covered in our 2028 furnace standard explainer.
How we researched this
Research date: October 8, 2026. We consulted 14 sources and cite seven, listed below; the four manufacturer documents are Tier 2, used only for their own equipment.
Excluded: Reddit and forums (combustion safety topic), the unsourced cost ranges and pressure ranges on page one of Google, and any installed price, since no federal series exists.
Frequently asked questions
Can a bad pressure switch cause a furnace not to turn on?
Yes. If the switch does not close after the inducer starts, the burners never light; if it reads closed before the inducer starts, the inducer never starts. Goodman logs these as E2 and E1, White-Rodgers as codes 31 and 23.
How do I know if my furnace pressure switch is bad?
A technician reads suction with a manometer and checks the contacts with an ohmmeter while the inducer runs. Suction above the switch rating with open contacts means a bad switch. Suction below it points to the vent, hose, drain or inducer, per Goodman.
What causes a pressure switch to be stuck open with the inducer running?
Weak suction at the hose. Goodman lists a blocked flue or inlet pipe, a blocked drain system, a weak inducer and a pinched hose. Rheem adds severe downdrafts, a leaky inducer gasket and an improperly sized vent. Fix the cause before replacing the switch.
Can water in the pressure switch hose stop a furnace?
Yes, on condensing furnaces. Water in the hose or a plugged port hides the suction. Goodman tells technicians to check the hose for kinks and moisture and to prime and clear the drain trap, and reserves drain service for qualified servicers.
Is it safe to run a furnace with the pressure switch jumped?
No. A jumpered switch lets burners fire without proof that exhaust is leaving. Rheem and Goodman both forbid bypassing safety controls. CPSC put heating system and water heater CO deaths at about 160 a year in its 2002 release. Call a technician instead.
How long does the furnace wait for the pressure switch to close?
It depends on the board. The Resideo S9200U1000 waits 150 seconds, idles five minutes and retries indefinitely. If the switch opens during prepurge, it holds the inducer on up to 60 seconds to re-close it. Other boards use different timings.
Sources
- Goodman Manufacturing. “Service and Troubleshooting, GM9S92/GM9S96/GC9S96, RS6612022r1.” https://mobile.goodmanmfg.com/mobileapp/stellent/pdf/infoPdf/Lit/RS6612022R1.pdf. Accessed October 2026.
- Rheem. “Installation Instructions, (-)801T Series, 92-24161-164-01.” https://resource.gemaire.com/is/content/Watscocom/Gemaire/rheem_r801t_en_ii.pdf. Accessed October 2026.
- Resideo. “S9200U1000 Integrated Furnace Control, Installation Instructions, 69-2075EF-07.” https://www.cochranesupply.com/media/assets/product/documents/Honeywell/S9200U1000.pdf. Accessed October 2026.
- White-Rodgers (Copeland). “50M56D-751 Control Kit, Installation Instructions.” https://media.copeland.com/7b1c16cb-45cd-45fe-8e23-b16b0109fc57/0037-7757001%20-%2050M56D-751%20Instruction%20Sheet%20(EF).pdf. Accessed October 2026.
- U.S. Department of Energy, Energy Saver. “Furnaces and Boilers” (archived copy). https://web.archive.org/web/2025id_/https://www.energy.gov/energysaver/furnaces-and-boilers. Accessed October 2026.
- eCFR. “10 CFR 430.32, Energy and water conservation standards.” https://www.ecfr.gov/current/title-10/chapter-II/subchapter-D/part-430/subpart-C/section-430.32. Accessed October 2026.
- U.S. Consumer Product Safety Commission. “CPSC Urges Seasonal Heating Systems Inspections to Prevent CO Deaths,” release 02-255, 2002. https://www.cpsc.gov/Newsroom/News-Releases/2002/CPSC-Urges-Seasonal-Heating-Systems-Inspections-to-Prevent-CO-Deaths. Accessed October 2026.
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