What does Carrier Furnace Blower Won't Shut Off - Causes & Fix mean?

Usually the thermostat fan switch is set to ON instead of AUTO, or the thermostat is sending a constant 24V signal to the G terminal.

How do I fix Carrier Furnace Blower Won't Shut Off - Causes & Fix?

Follow the step-by-step diagnosis below. The most likely fix is identified by checking power, sensor resistance, and control-board signals in order — using a multimeter and the part numbers documented in the parts reference table.

Can I keep running the equipment with this fault active?

Generally no. Faults on Hvac units are emitted when a sensor, safety, or control circuit is outside its operating envelope. Running through an active fault risks compressor, heater, or control-board damage. Diagnose and clear the fault first.

What part is most commonly replaced for Carrier Furnace Blower Won't Shut Off - Causes & Fix?

The most frequently replaced parts for Carrier Furnace Blower Won't Shut Off - Causes & Fix are listed in the Parts Reference section of this guide with OEM part numbers and typical price ranges. Check the table for direct replacements.

Is Carrier Furnace Blower Won't Shut Off - Causes & Fix a DIY repair or do I need a technician?

Sensor swaps, fan motor replacements, and condenser cleaning are typical DIY-level repairs. Anything involving refrigerant, gas, or high-voltage (>240V) work requires a licensed technician for both safety and code-compliance reasons.

Carrier Furnace Blower Won't Shut Off - Causes & Fix

Carrier Furnace Blower Won’t Shut Off — What’s Happening

A Carrier furnace blower that won’t shut off means the indoor blower is being told to keep running or the blower relay or control is stuck closed. This is not a single fault code but a symptom with several possible causes. The blower runs continuously even when there is no heating or cooling call, which points to either a control signal keeping it energized or a mechanical failure in the switching component.

Jump to Fix

Most Likely Causes

Thermostat fan setting on ON instead of AUTO The thermostat fan switch is in the ON position, which commands continuous blower operation regardless of heating or cooling demand.
Thermostat failure or internal switching fault The thermostat itself is malfunctioning and sending an unwanted 24V fan signal to the G terminal at the furnace even when no call is present.
Shorted or damaged thermostat wire A short between the G wire and the R (24V) wire in the thermostat cable energizes the blower circuit continuously.
Stuck fan relay or welded contacts on control board The relay on the furnace control board that switches blower power has welded contacts or is stuck in the closed position, keeping the blower energized.
Failed fan limit control or sequencer On systems using a fan limit control or sequencer to switch the blower, the component has failed with contacts stuck closed.
ECM blower motor module failure On furnaces with electronically commutated motors, the motor control module itself can fail and prevent proper shutoff even with correct control inputs.
Overheating condition or tripped safety switch A dirty filter or blocked airflow has caused overheating and abnormal system operation, or a manual-reset rollout switch on the burner box has tripped and the system is behaving erratically.

How to Diagnose and Fix

Check the thermostat fan setting and confirm it is set to AUTO, not ON.
Remove the thermostat from its wall base and observe whether the blower stops running (if it does, the thermostat or its wiring is the source).
Measure voltage between the G and C terminals at the furnace control board with no heating or cooling call active (a present 24V signal means the blower is being commanded on).
Disconnect the thermostat wiring at the furnace and recheck for 24V at G to isolate whether the issue is the thermostat, the wiring, or the furnace control.
Inspect the thermostat cable for damaged insulation, shorts, or miswiring between G, R, and other low-voltage terminals.
Inspect the fan relay on the control board or any external sequencer or fan limit control for welded or stuck contacts and replace the board or component if found.
Replace the furnace air filter if dirty and verify that return and supply airflow paths are clear and unobstructed.
Check the manual-reset rollout switch on the burner box and reset it only after correcting the airflow or overheating cause that led to the trip.

Parts You Might Need

Part	Notes
Furnace control board	Amazon \| Replace if the fan relay has welded contacts or is stuck closed.
Thermostat	Amazon \| Replace if internal switching is faulty or it sends a constant G signal.
ECM blower motor module	Amazon \| Required if the motor itself will not shut off despite proper control inputs.
Thermostat wire cable	Amazon \| Replace if shorted or damaged between terminals.

If your appliance also shows a code on the display, these match this problem:

When to Call a Pro

Call a professional if you are not comfortable working with 24V control wiring or 120V blower circuits, if the control board or blower motor module needs replacement, or if a rollout switch continues to trip after you have corrected airflow issues. Any work involving gas burners, ignition components, or repeated safety trips should be handled by a qualified HVAC technician. For gas line, burner, or igniter work, or if you ever smell gas, stop and call a licensed technician.