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

Usually the thermostat fan switch is set to ON instead of AUTO, or there's a shorted wire between R and G creating a constant fan call.

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

The most frequently replaced parts for Rheem 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 Rheem 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.

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

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

A Rheem furnace blower that won’t shut off means the system is receiving a continuous call for fan operation, or the control circuit, relay, or ECM blower module has failed so the blower stays energized even when the thermostat is satisfied. This is not a single diagnostic code in Rheem’s fault list. It’s a symptom that must be traced to the thermostat, wiring, control board, fan limit control, or ECM blower motor depending on your model.

If the blower runs continuously in heat, cool, or with the thermostat set to Auto, the furnace is being told to keep the fan on or the fan-control component is stuck closed. If the blower continues after the thermostat is removed or disconnected, the issue is more likely in the furnace control wiring, control board, fan relay, fan limit control, or ECM module rather than the thermostat itself.

Jump to Fix

Most Likely Causes

Thermostat fan switch set to ON The fan switch is in the ON position instead of AUTO, which intentionally runs the blower continuously.
Shorted thermostat wiring A short or false call between R and G wires creates continuous blower demand, and one training case found measurable continuity between R and G when there should have been none.
Thermostat face or control failure The thermostat head itself is stuck or faulty, and removing the thermostat head makes the blower stop.
Stuck fan relay or control board output The integrated furnace control or a fan relay on the board is stuck closed, holding the blower on even when no call is present.
Faulty fan limit control On furnaces that use a fan/limit switch rather than an ECM-controlled blower, the limit control may be stuck or out of range.
ECM blower motor or module failure The motor’s internal electronics or ECM module can fail and keep the blower running or prevent proper shutdown.
Bad motor wiring or loose connections Damaged harnesses, loose plugs, or burned connectors in the blower compartment can create false signals or power loops.

How to Diagnose and Fix

Verify the symptom by checking whether the blower runs with the thermostat in Fan Auto and with no call for heat or cool.
Pull the thermostat face or disconnect the thermostat wires at the furnace. If the blower stops, troubleshoot the thermostat or thermostat base and wiring first.
Inspect thermostat wiring for damage, miswiring, or continuity between R and G when power is off. Continuity there indicates a shorted fan call circuit.
Check the furnace control board for a stuck fan relay or incorrect output to the blower motor.
On models with a fan limit control, test the control’s settings and operation. If it is out of range or sticking, replace it.
On ECM systems, verify line voltage (115 volts between L1 and Neutral at the Integrated Furnace Control) at the blower motor, then isolate the motor and module from the board to determine whether the motor, module, or control signal is the cause.
Inspect the blower compartment for loose plugs, damaged harnesses, or burned connectors before replacing parts.
After diagnosis, replace only the failed component: thermostat, thermostat wire, control board, fan limit control, or ECM motor and module.

Parts You Might Need

Part	Notes
Thermostat or thermostat face assembly	Amazon \| If removing the head stops the blower
Integrated furnace control board	Amazon \| When fan relay is stuck or output is faulty
Fan limit control	Amazon \| For non-ECM furnaces with mechanical fan/limit switches
ECM blower motor or motor module	Amazon \| When motor electronics fail and blower won’t stop

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

When to Call a Pro

Call a technician if you’ve confirmed the thermostat fan switch is in AUTO, disconnecting the thermostat does not stop the blower, or you are not comfortable working with 115-volt furnace control circuits. Control board diagnostics, ECM motor isolation, and fan limit control replacement require meter testing and access to the blower compartment. Any work involving gas burners, ignition, or internal furnace wiring 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.