A gas furnace has two motors that move air, and they fail in different places in the heating sequence. The inducer motor pulls combustion gases through the heat exchanger and vent before the burners light. The blower motor moves house air across the heat exchanger and through the ducts. A no-heat call can be either, and a pressure switch that will not close makes an inducer problem look like a blower problem. This page separates the two by what happens, and in what order, when the thermostat calls for heat. United sells the blower motor only; there are no inducer motors in the catalog.
Key Takeaways
- The inducer runs first and proves draft through the pressure switch. The blower starts only after ignition, on a delay.
- If the burners never light, work the inducer, pressure switch and vent. If the burners light and the air never arrives, work the blower.
- A pressure switch that stays open is a symptom. A failed inducer is one cause, but so are blocked vents, cracked tubing and condensate backup.
- Do not replace a pressure switch or a motor without finding the cause. A blower motor is confirmed by voltage, command and a winding test, not by elimination alone.
- United sells remanufactured ECM blower motors only. It does not sell inducer motors.
What Each Motor Does in the Heating Sequence
Manufacturer sequences vary in timing, but the order is consistent. The following comes from Bryant's two-stage furnace manual and Amana's integrated ignition control manual.
- Call for heat. The control starts the inducer. The inducer creates draft in the combustion chamber and vent.
- Draft is proven. The pressure switch closes. In Bryant's sequence, once the low-heat pressure switch closes, the control begins a 15-second prepurge. If the switch does not close, Amana's control keeps the inducer on and waits for it.
- Ignition. At the end of prepurge, the hot surface igniter is energized for a 17-second warm-up, and the gas valve opens. Bryant allows a 2-second flame-proving period, and retries ignition if flame is not proved.
- Blower on. The blower starts after the gas valve opens. Bryant's low-heat sequence turns it on 45 seconds after the valve opens, and Amana's starts it about 30 seconds after ignition is confirmed. The delay lets the heat exchanger warm before the blower moves air.
- Shutdown. The inducer runs a short post-purge, and the blower keeps running through an off-delay. Amana lists an adjustable blower off-delay of 60, 90, 120 or 180 seconds.
The first three steps belong to the inducer side. Step four is the blower. The timing in your furnace is in its installation manual; use it, not this page, for exact seconds.
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Symptoms That Separate Them
| What you observe | Where the sequence stopped | Look at first |
|---|---|---|
| Thermostat calls, nothing starts, no inducer sound, no igniter | Before the inducer | Power, door switch, control, inducer voltage and winding |
| Inducer runs, burners never light | Draft not proven | Pressure switch, tubing, vent, condensate, inducer output |
| Inducer runs, igniter glows, burners never light | Past draft, at ignition | Igniter, gas valve, flame sensing |
| Burners light, blower never starts, burners shut off after a few minutes | Blower | Blower power and command, motor windings, wheel |
| Burners light, blower runs, little air | Air path | Wheel, filter, ducts, speed setting |
The blower row is the one United's motors answer. Burners that light and a blower that does not follow is the signature: the heat exchanger has no air moving across it, so its temperature climbs until a limit control opens. Amana's sequence describes the limit response: if a primary or auxiliary limit opens, the inducer runs briefly and then the blower runs until the limit closes. A furnace that fires, shuts down and cycles again without moving air is a blower motor candidate. For a blower that runs but the system is not heating, see furnace blower runs constantly but no heat, and for the split between a running system and a dead blower, the system runs but the blower doesn't.
Pressure Switch Faults That Look Like Blower Faults
From the customer's side, a furnace that does not heat is a furnace that does not heat. A homeowner hears the inducer, sees no flame and feels no air, and calls it a blower problem. The pressure switch is the reason. HVAC School describes it as a normally open switch that closes when the inducer creates negative pressure, tubed to the heat exchanger or the inducer housing. If the switch does not close before ignition, the control will not allow ignition, and the blower never gets its turn.
The same source lists the causes of a switch that stays open: a failed inducer, a blocked chimney or flue, animal nests, condensate backup, a partly blocked secondary heat exchanger, and loose or bad wiring, with a bad switch listed as the least common. Its method is to slow down and check incoming voltage and inducer amp draw against the data tag, inspect the tubing for cracks, brittleness, crud or water, read draft with a manometer against the switch's closing pressure, and on 90%+ furnaces check the condensate trap and drain. It also cautions against replacing the switch without finding the root cause, since callbacks follow.
The fault code displayed on the control narrows the circuit further. Codes differ by manufacturer, so use the Carrier furnace and AC codes article or the HVAC fault code lookup rather than a list here.
The 3-Step Check Before You Order
- Watch the sequence. Start a heat call and note how far it gets. No inducer: stop here, the blower is not the problem. Inducer and igniter but no flame: stop here. Flame and no blower after the delay in the installation manual: continue.
- Confirm power and command at the blower. With the burners lit, measure line voltage at the motor and confirm the heat speed command from the control. On an X13, that is 24 VAC on the active tap. On the 2.3, EON and 3.0, the command comes from the control, and a TECINspect reads the motor. Voltage and command present, no rotation: the motor is suspect. No command: the control is. The full ECM sequence is in how to test an ECM blower motor.
- Test the windings. Power off, motor disconnected: windings under 20 ohms and balanced, and 100k ohms or more to the shell. A pass clears the motor and points to the control. A fail means the motor.
Spin the wheel by hand with the power off and check that it is tight on the shaft. A wheel that binds or slips will mimic a failed motor. The wheel and airflow checks are in blower running but no airflow.
United Sells the Blower Motor Only
United HVAC Motors sells remanufactured ECM blower motors, programmed to the OEM part number, shipped from Tampa, Florida. United does not sell inducer motors, pressure switches, control boards, loose ECM modules, PSC motors or condenser fan motors. If the check above lands on the inducer, that part comes from another source. If it lands on the blower, match the nameplate in the ECM motor cross reference and shop the family: X13, ECM 2.3, EON or ECM 3.0. Motors start from $329.99 with Same Day Processing, free 1-2 day shipping and a 2-Year Replacement Warranty.
FAQs
What is the difference between an inducer motor and a blower motor?
The inducer motor pulls combustion gases through the heat exchanger and vent before and during firing. The blower motor moves house air across the heat exchanger and through the ducts. The inducer runs first; the blower starts after ignition.
Can a bad inducer motor stop the blower from running?
Yes. If the inducer fails to prove draft, the pressure switch stays open, the control will not ignite the burners, and the blower never gets its call to start.
How can a tech tell the blower motor failed and not the inducer?
If the inducer runs, the burners light, and the blower does not start after its delay, the blower side is the suspect. Confirm voltage and command at the motor, then test the windings.
Does a pressure switch fault mean the inducer is bad?
Not necessarily. A failed inducer is one cause, but blocked vents, cracked or plugged tubing, condensate backup and wiring problems also keep the switch open. Find the cause before replacing parts.
Does United sell inducer motors?
No. United sells remanufactured ECM blower motors only.
