Component
Inducer motor
The inducer is the small blower that starts before ignition to pull combustion air through the heat exchanger and push flue gas out the vent. When it fails or slows, the pressure switch cannot close and the furnace will not light. Two-stage furnaces use a two-speed inducer.
Short answer
If the furnace does nothing after the thermostat calls except perhaps a hum, or the inducer runs but the pressure switch never closes, the inducer or its wheel may be at fault. Symptoms include grinding or squealing at start-up, a motor that is hot to the touch, or an inducer that starts only on some calls. Diagnosis includes checking voltage to the motor, the wheel, and the draft it produces.
Role in the ignition sequence
On a call for heat the control energizes the inducer first. Only when the pressure switch proves draft does the control move on to heating the ignitor and opening the gas valve. On Carrier's 59TP6C the control runs the inducer at high speed during pre-purge and then chooses low or high speed for the heating stage.
Because the inducer runs every cycle and lives in the hottest, wettest part of a condensing furnace, its bearings and wheel are among the more common wear items after ten or more years.
Symptoms
Loud or changing noise at start-up, especially a scraping or grinding that fades as the motor warms.
Pressure-switch codes that come and go, particularly on high fire, where the inducer needs its highest speed.
No inducer start at all: often a failed motor or capacitor, sometimes a control problem.
Water inside the inducer housing from a blocked trap, which corrodes the wheel and shaft over time.
Documented codes that point here
- Carrier 59SC6A status code 31: secondary pressure switch open or lockout
- Carrier 59SC6A status code 32.1: open main pressure switch (LPS)
- Carrier 59SC6A status code 33.1: a switch has opened in the main limit circuit
- Carrier 59SC6A status code 13: limit lockout or ignition lockout
- Carrier 59TP6C status code 31: high-heat pressure switch (HPS) open or slow to close
- Carrier 59TP6C status code 13: limit lockout or ignition lockout
- Carrier 59TP6C status code 14: flame-loss lockouts during a heat request
- Carrier 59TP6C status code 23: pressure switch stuck closed
- Carrier 59TP6C status code 32.2: open main pressure switch (LPS)
- Carrier 59TP6C status code 33: limit circuit, high-heat or ignition lockout
- Carrier 59TP6C status code 43.1: HPS closed before LPS
- Carrier 59TP7A status code 31: high-heat pressure switch (HPS) open or slow to close
- Carrier 59TP7A status code 13: limit lockout or ignition lockout
- Carrier 59TP7A status code 14: flame-loss lockouts during a heat request
- Carrier 59TP7A status code 23: pressure switch stuck closed
- Carrier 59TP7A status code 32.2: open main pressure switch (LPS)
- Carrier 59TP7A status code 33: limit circuit, high-heat or ignition lockout
- Carrier 59TP7A status code 43.1: HPS closed before LPS
- Carrier 59SP6B status code 31: secondary pressure switch open or lockout
- Carrier 59SP6B status code 32.1: open main pressure switch (LPS)
- Carrier 59SP6B status code 33.1: a switch has opened in the main limit circuit
- Carrier 59SP6B status code 13: limit lockout or ignition lockout
- Carrier 59TN7A status code 31: high-heat pressure switch (HPS) open or slow to close
- Carrier 59TN7A status code 13: limit lockout or ignition lockout
- Carrier 59TN7A status code 14: flame-loss lockouts during a heat request
- Carrier 59TN7A status code 23: pressure switch stuck closed
- Carrier 59TN7A status code 32.2: open main pressure switch (LPS)
- Carrier 59TN7A status code 43.1: HPS closed before LPS
- Carrier 59TN7A status code 33.1: a switch has opened in the main limit circuit
Related
Questions people ask
Can an inducer be repaired?
It is usually replaced as an assembly. Some furnaces let the motor be replaced separately from the housing; the technician confirms the part for your exact model number.
Is an inducer failure covered by warranty?
It is a part, so it may be within the parts warranty if the furnace is registered and the failure is not caused by installation or maintenance issues. Labour is usually separate. Check the manufacturer's certificate.
Need this looked at?
Call BC Wide with the brand, model number and anything on the display. Or
Request service online with this page attached.