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Carrier Furnace Not Heating


The part(s) or condition(s) listed below for the symptom Furnace not heating are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.

Most Frequent Causes for Furnace not heating

Cause 1Igniter

The igniter gets very hot and glows bright orange to light the gas burner. If the igniter fails or cracks, the furnace won’t heat. To determine if the igniter is faulty, remove the igniter and inspect it for cracks. If the igniter is cracked, replace it. If the igniter is not cracked, use a multimeter to test the igniter for continuity. If the igniter does not have continuity, replace it.

Igniter for your CarrierFurnace
Igniter - Part # 2347588 Mfg Part # 332505-751

Igniter replacement kit

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Cause 2Flame Sensor

The flame sensor monitors the burner to detect whether or not a flame is present. If the flame sensor is defective, it might fail to detect a flame. If the flame sensor does not detect a flame, the control board will shut off voltage to the gas valve to prevent the furnace from heating. Sometimes, if the flame sensor is dirty, it will fail to detect a flame. Try cleaning the flame sensor with a fine abrasive pad. If the furnace still doesn’t heat, replace the flame sensor.

Flame Sensor for your CarrierFurnace
Flame Sensor - Part # 2347745 Mfg Part # LH680014

Furnace flame sensor. The flame sensor monitors the burner to detect whether or not a flame is present. If the flame sensor is defective, the furnace may not heat.

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Cause 3Draft Inducer Motor

The draft inducer motor draws air into the heat exchanger and then exhausts it out the flue. The pressure switch senses a pressure change and closes a switch to signal the control board that the furnace has proper air flow. If the draft inducer motor is defective, it may be unable to close the pressure switch, causing the ignition process to stall and the furnace to shut off after a few minutes. If the ignition process stalls, the furnace will shut off. If the draft inducer motor is at fault, replace it.

Draft Inducer Motor for your CarrierFurnace
Draft Inducer Motor - Part # 2347563 Mfg Part # 318984-753

Furnace draft inducer motor with cooling fan. Be aware that the screw holes are not threaded—you will need to use self-tapping screws to install the motor.

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Cause 4Control Board

The control board regulates the power supply to all of the components of the furnace. If the control board fails, it might not send voltage to the ignition system, causing the furnace not to heat.

Control Board for your CarrierFurnace
Control Board - Part # 2347573 Mfg Part # 325878-751

Furnace control board.

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Cause 5Gas Valve Assembly

The gas valve opens to allow gas to flow into the burner. If the gas valve is defective, the valve will not open, preventing the furnace from heating. To determine if the gas valve is at fault, use a multimeter to test it for continuity. If the gas valve does not have continuity, replace it.

Gas Valve Assembly for your CarrierFurnace
Gas Valve Assembly - Part # 2347634 Mfg Part # EF660015

Gas valve kit. *Should be installed by a certified Carrier repairperson.

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Cause 6Pressure Switch

The pressure switch closes when the burner has sufficient airflow. If the pressure switch isn’t working, it might not close when the proper airflow is present, causing the ignition process to stall. To determine if the pressure switch is defective, use a multimeter to test the switch for continuity. If the pressure switch does not have continuity, replace it.

Pressure Switch for your CarrierFurnace
Pressure Switch - Part # 2347698 Mfg Part # HK06WC090
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Cause 7Gas Supply Problem

Check the gas valve to ensure that it is turned on. If the furnace uses propane, check to see if the furnace has run out of gas.

Cause 8Air Flow Problem

The furnace must have proper airflow through the burner in order to continue running. The furnace draws air from the surrounding area or from outside the room. If the furnace is located in a utility closet or in a cramped storage room, there may not be sufficient available air for the furnace to heat properly. If the furnace draws air from outside the home, check for an obstructions at the air inlet.

Cause 9Incoming Power Problem

Check to see if there is power to the furnace. If there is no power to the furnace, check the furnace circuit breaker or fuse.