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HomeRepair HelpFurnace RepairFurnace blower runs all the time Repair
Furnace blower runs all the time
01 - Furnace Control Board
The control board has relays that regulate the voltage to each component in the furnace. If the relay that controls the blower motor fails while it is closed, it will send continuous voltage to the blower motor, causing the motor to run continuously. If the control board is at fault, replace it.
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Highly Likely
02 - Furnace Wifi Thermostat
The WiFi thermostat has electrical contacts that control the power supply to the furnace. If the contact that controls the blower motor sticks closed, it will send continuous voltage to the blower motor, causing the motor to run continuously. To determine if the thermostat is defective, use a multi-meter to test it for continuity. If the WiFi thermostat shows continuity between the (R) and (G) terminals when the thermostat is in the off position the thermostat has failed and will need to be replaced.
Common
03 - Furnace Wall Thermostat
The wall thermostat has electrical contacts that control the power supply to the furnace. If the contact that controls the blower motor sticks closed, it will send continuous voltage to the blower motor, causing the motor to run continuously. To determine if the thermostat is defective, use a multi-meter to test it for continuity. If the wall thermostat shows continuity between the (R) and (G) terminals when the thermostat is in the off position the thermostat has failed and will need to be replaced.
Less Common
04 - Fan Mode set to "Fan On"
The furnace blower will run continuously if the thermostat mode is set to “Fan On”. To prevent the blower from running continuously, set the fan mode to "Auto" or turn it off if heating or cooling is not required.
Less Common