What does an inducer motor do? A furnace inducer motor spins a small blower that pulls combustion gases through the heat exchanger and pushes them into the vent. It must prove that draft before the burners can light, then runs through the whole heating cycle and a short post-purge.
Key Takeaways
- Rheem says the inducer is used to “pull flue products through the combustion chamber” (Rheem 801T instructions).
- DOE ties the exhaust fan to mid-efficiency furnaces rated 80% to 83% AFUE (DOE Energy Saver, archived copy).
- Pre-purge runs 15 seconds on a Lennox SL280UHV and 25 seconds on a Carrier 58MVP, not a minute (Lennox 508245-01).
- 23 of 24 Fasco replacement inducer sheets we pulled list a shaded pole motor, not a capacitor-run PSC (Fasco product packets).
- Goodman says inducer bearings are permanently lubricated, and Rheem warns oil can void the warranty (Goodman RS6612022).
- More than 200 people in the US die yearly from non-fire CO poisoning tied to consumer products (CPSC).
What does an inducer motor do in a furnace?
The inducer motor, also called a draft inducer, venter or combustion air inducer, creates the draft that moves exhaust out of a gas furnace.
A fan-assisted Category I furnace, Rheem says, “operates with a nonpositive vent pressure” with vent gas at least 140°F above its dew point. Condensing furnaces, 90% to 98.5% AFUE per DOE, use an inducer too; see our guide to furnace vent pipe rules.
Its suction closes the pressure switch, and Goodman starts pre-purge only once that switch is “detected closed.” Our pressure switch explainer covers that handshake.
When does the furnace inducer motor run, and for how long?
The furnace inducer motor starts first on every call for heat and stops last. Burners light about 30 to 45 seconds after the pressure switch proves draft on the furnaces we checked, then the inducer runs the entire burn and a post-purge of 5 to 15 seconds.
Lennox’s SL280UHV runs a 15 second pre-purge on low speed plus a 20 second ignitor warm-up, about 35 seconds. Carrier’s 58MVP takes 25 seconds plus 17 seconds, or 42 seconds. The White-Rodgers 50M56D-751 board pairs a 15 second pre-purge with an adaptive warm-up of 5 to 21 seconds starting at 17, about 32 seconds.
Post-purge is 15 seconds on Goodman and 5 seconds on Lennox. A furnace that restarts within minutes is a different fault; see furnace short cycling.
Myth: the inducer runs a full minute before the burners
Not on the furnaces we checked: pre-purge runs 15 to 25 seconds once draft is proven. A minute of inducer noise with no flame is a fault. Rheem’s 801T locks out for five minutes if its switch fails to close after 60 seconds.
What kinds of draft inducer motor are there?
The four kinds of draft inducer motor are single-speed shaded pole, single-speed permanent split capacitor (PSC), two-speed and variable-speed. Most replacements are shaded pole, so capacitor advice applies only to the PSC kind.
We pulled 24 Fasco (Regal Beloit) OEM-replacement inducer sheets by model number: 23 of 24 list a shaded pole motor, and only the A136 is PSC, at 115 V and 3450 rpm. All list the motor as thermally protected, so an overheated inducer can stop and later restart.
| Type | Named example | What the maker document shows |
|---|---|---|
| Single-speed shaded pole | Fasco A138, 120 V | 0.7 A, 3000 rpm, no capacitor listed |
| Single-speed PSC | Fasco A136, 115 V | 0.75 A, 3450 rpm, capacitor-run |
| Two-speed | Lennox SL280UHV | Low speed for pre-purge and low fire, high speed for high fire |
| Variable-speed | Carrier 58MVP | Inducer RPM is used to evaluate vent system resistance |
| Variable-speed, calibrating | Rheem 801T ultra low NOx | Ramps 25 RPM every 4 seconds to calibrate, once every 100 heat calls |
What are the symptoms of a bad inducer motor?
The symptoms of a bad inducer motor are no ignition, a hum without spin, a squeal or rattle, a motor that runs and quits, or an inducer fault code. Match the symptom to its check before blaming the motor.
| Symptom | Check first | Document |
|---|---|---|
| Inducer never starts, silent | 115 V at the motor during trial for ignition, then winding continuity | Goodman RS6612022 |
| Hums but does not spin | Wheel turns freely with power off; capacitor only on a PSC model | Fasco K674, Fasco A136 |
| Squeal, grind or rattle | Wheel position on the shaft, mounting screws, dust on windings | Fasco K674, Goodman |
| Runs, stops, restarts | Thermal protector tripping on an overheating motor | Goodman flowchart, Fasco packets |
| Runs but no ignition | Draft not proven: vent, hose or inducer gasket | Rheem 801T |
| Water or gurgling in the housing | Condensing furnace drain system | Goodman flowchart |
| Code 34 or code 71 (Rheem), E228 (Lennox) | Inducer overcurrent, inducer fault, inducer calibration failure | Rheem 801T, Lennox 508245-01 |
Do not oil a squealing inducer. Goodman says the bearings are permanently lubricated, and Rheem warns that lubricants “can reduce the motor life and void the warranty.” See our guide to furnace noises worth shutting down for.
On a 90% furnace, Goodman’s flowchart tells techs to check for condensate in inducer and the drain system, the same path behind a furnace leaking water.
Why does the inducer motor run but the furnace won’t light?
When the inducer motor runs but the furnace won’t light, the control has not seen enough proven draft, so it never powers the igniter. Rheem’s 801T lists six causes: an inoperative induced draft blower, a leaky switch hose, a blocked vent, severe downdrafts, a leaky gasket at the induced draft blower, and an improperly sized or installed vent.
Goodman’s flowchart also has techs check inducer voltage and amperage against spec before replacing a switch. If draft proves and ignition still fails, follow our furnace ignition sequence guide and the hot surface igniter tests.
How do technicians test an inducer motor?
Technicians test an inducer motor by checking line voltage at the motor, testing the windings with power off, then measuring running current. Goodman’s service manual sets this order so the board, wiring and vent are ruled out before the motor is condemned.
- Note the flash or display code; our control board code guide explains counting.
- On a call for heat, check for 115 V at the inducer during trial for ignition. Goodman: no voltage means the “control board or wiring to inducer is defective.”
- Power off, check continuity between leads and from each lead to the frame. A broken winding or a reading to ground means replace the motor.
- Voltage present but no rotation: replace it, after ruling out the thermal protector and over-voltage.
- Running, compare amperage to the motor rating; the White-Rodgers 50M56D-751 inducer relay is rated 2.8 A at 120 VAC.
- Clear dust from the windings, which Goodman says “may cause overheating.”
This is live 115 V work in a gas appliance; Fasco’s K674 guide leaves everything beyond filters and coils to trained, licensed personnel. Owners can use our furnace reset guide.
What does inducer motor replacement involve?
Inducer motor replacement means fitting the exact OEM part or the maker’s listed kit, renewing every seal and proving a full heating cycle. The inducer sits on the flue side, so a poor seal can leak exhaust.
The York inducer kit S1-32434558000 matches a color-coded restrictor to each furnace model and has the four screws torqued to about 30 in-lbs so the inducer “does not leak.” Fasco’s K674 kit for Carrier and Bryant furnaces says to move any shaft seal to the new assembly and use only the original mounting screws, since longer ones can strike the wheel.
- Shut off power and gas; photograph the wiring.
- Install the new gasket, restrictor and seals exactly as the kit shows; Lennox says the gasket “should be left in place” even when the inducer is only rotated.
- Reattach the vent; Rheem requires predrilled 1/8 inch holes and #8 screws at the inducer collar.
- Run the board self-test before calling for heat, then one complete heating cycle, as K674 directs.
Safety: a leaking inducer seal is a carbon monoxide path
Rheem warns that skipping its collar fastening steps “can cause recirculation of flue products causing carbon monoxide poisoning.” CPSC calls CO a colorless, odorless, poisonous gas. Keep alarms placed per our CO detector placement guide sets out.
We publish no replacement price: no federal or national lab series tracks inducer repairs, and page one’s ranges trace to contractor quotes. For whole furnaces, see our federal furnace cost estimates.
How we researched this
Researched October 11, 2026. We read Goodman, Rheem, Lennox and Carrier furnace manuals, the White-Rodgers 50M56D-751 sheet, York and Fasco kit instructions, 24 Fasco spec packets, DOE and CPSC; all are cited. The Fasco sample was pulled by model number, not at random. Maker figures are maker claims, not our tests, and the Carrier guide is a third-party mirror. Excluded: prices (no federal series), contractor blogs, auto-generated manual sites, and Reddit, because this is a combustion and carbon monoxide safety topic. Timing totals are our arithmetic.
Frequently asked questions
Will a furnace run without an inducer motor?
No. Goodman’s control starts pre-purge only once the pressure switch is detected closed, and the inducer’s draft is what closes it. Rheem lists an inoperative induced draft blower first among reasons the switch stays open. Jumpering the switch to run without draft defeats a combustion safety and is never a fix.
How much does it cost to replace an inducer motor?
We print no figure, because no federal or national lab source tracks inducer repair prices. The cost drivers are whether a motor-only kit such as Fasco’s K674 fits or a full OEM assembly is needed, the model-matched restrictor and gasket parts, and labor for the full heating-cycle test.
Does an inducer motor have a capacitor?
Only the PSC kind. In our sample of 24 Fasco replacement inducer sheets, 23 of 24 list a shaded pole motor and only the A136 lists a permanent split capacitor motor. Read the motor label before buying a capacitor, since a shaded pole sheet lists none.
Can I oil a noisy inducer motor?
No. Goodman says inducer bearings are permanently lubricated by the manufacturer, and Rheem says lubricants can reduce motor life and void the warranty, so a squealing bearing is replaced, not oiled. Goodman does advise checking the windings for dust, which may cause overheating.
Why is there water in my inducer motor?
On a condensing furnace, water in the inducer points first to the drain system. Goodman’s flowchart tells techs to check for condensate in the inducer when the pressure switch will not close, and to check the drain on 90% furnaces. Goodman marks drain service “QUALIFIED SERVICER ONLY.”
Can I replace an inducer motor myself?
Manufacturers say no. Fasco’s K674 guide says heating equipment should only be installed and serviced by trained personnel because of gas and electrical hazards. The job involves model-matched restrictors, gaskets and torque values, as in York’s S1-32434558000 kit, where a mistake can leak flue gas.
Sources
- Goodman (Daikin). “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 Upflow Series Gas Furnaces.” https://resource.gemaire.com/is/content/Watscocom/Gemaire/rheem_r801t_en_ii.pdf. Accessed October 2026.
- Lennox. “SL280UHV Installation Instructions, 508245-01.” https://www.lennox.com/dA/0891b8032a/508245-01b.pdf. Accessed October 2026.
- Carrier. “58MVP Service and Troubleshooting Guide,” third-party mirror. https://www.manualsdir.com/manuals/63165/carrier-58mvp.html?page=2. Accessed October 2026.
- Copeland (White-Rodgers). “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.
- Johnson Controls (York). “Inducer Replacement Kit S1-32434558000.” https://www.industrialstores.com/media/industrialstores/product/attachments/York-S1-32434558000-Draft-Inducer-Accessory-Kit-Installation-Instruction.pdf. Accessed October 2026.
- Fasco. “K674 Installation and Operation Guide.” https://www.electricmotorwarehouse.com/content/PDF/K674_instructions.pdf. Accessed October 2026.
- Regal Beloit (Fasco). “Product Information Packets,” 24 draft inducer models (A136 shown). https://shop.dreisilker.com/content/fasco-data/A136/spec-sheet/A136-spec-sheet.pdf. Accessed October 2026.
- U.S. Department of Energy. “Furnaces and Boilers,” archived copy. https://web.archive.org/web/2025id_/https://www.energy.gov/energysaver/furnaces-and-boilers. Accessed October 2026.
- U.S. Consumer Product Safety Commission. “Carbon Monoxide Information Center.” https://www.cpsc.gov/Safety-Education/Safety-Education-Centers/Carbon-Monoxide-Information-Center. Accessed October 2026.
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