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Carrier Furnace Not Turning On? 9 Common Causes (+ Fixes)

Your carrier furnace not turning on could be due to a clogged filter, cracked igniter, faulty thermostat, tripped circuit breaker, or a faulty flame sensor. Cleaning the air filter and replacing the faulty thermostat, flame sensor, and igniter are possible solutions.

Nothing is as troublesome as the carrier furnace not turning on, especially during the cold season. Therefore, we troubleshoot why your furnace is not turning on in this article and provide solutions.

Troubleshooting Basics

Carrier Furnace not Turning On 9 Common Causes Fixes

Before concluding that your carrier furnace is not turning on because of a problem, ensure you’ve covered the basics. Have you switched the power on and set your furnace setting to heat?  

You can check the following areas once you’ve confirmed that the power and furnace settings are on. Remember that a faulty heating system might cause you to incur hefty utility bills. 

Your furnace control board will indicate the following error codes. 

Error CodeMeaning
14Ignition lockout
22Setup error
Blinking yellow 3The furnace is stuck in high-fire mode.
Blinking green 4It is stuck in low-fire mode.
12Blower calibration lockout.
22Set up error

We explain everything you need to know about carrier furnace not turning on. 

1. Checking the Thermostat

Thermostat for a furnace 

Start by confirming that the power is getting to the thermostat. The command center for your furnace is the thermostat. 

Potential thermostat problems are:

  • Low or dead batteries: Another problem could be that the batteries are dead. Hence, no signal is being sent from the thermostat to the furnace. 
  • Power cables: Some thermostats use power cables instead of batteries. The cables could be improperly connected or damaged. 
  • Furnace fan: The fan is in “off” mode. Thus, it’s not coordinated with the heating cycle of the carrier furnace. 


Buy new batteries or replace the damaged power cables. Reinstall any loose wires. 

Switch the fan to “on” or “auto”.  Inspect the cables that connect the fan switch to the rest of the system to see if the fan is on /in auto-position but is not functioning. Fix any loose wires or replace damaged ones. 

Always set the temperature on the thermostat to be above the indoor temperature. 

2. Inspecting the Power Source

A circuit board 

Check whether the power is on, which might be the main reason. A faulty furnace transformer will prevent the carrier furnace from turning on. 

The main circuit board regulates the power supply to all furnace components. If the board fails, no voltage is sent to the ignition system. 


Locate where your power supply switch is and put the power on. The metal cabinet that contains the blower unit is where most of the power switches are. 

However, if after 2-3 minutes of switching on the power supply, the furnace does not turn on, then the furnace transformer might be faulty. Replace the furnace transformer. 

3. Examining the Circuit Breakers

 A circuit breaker

Check the circuit breaker to confirm that the furnace is getting enough power. Confirm that the fuse box hasn’t tripped a circuit breaker. 

A circuit breaker prevents a power surge from damaging the furnace. Most units have a circuit breaker for the outdoor unit and another for the indoor unit. You need to flip both circuit breakers. 


If the circuit breaker has tripped, flip it over to reset it. Use the owner’s manual if unsure where the breaker switch is. 

The furnace might take a few minutes to power back. Hence, no need to call and question your technician immediately.

However, if the unit trips again after this, you should call a professional with the right knowledge to sort out your power problems. 

Confirm that the wire inside the fuse is intact. If not, replace the fuse with the same rating. 

If you need help in replacing the fuse, you can watch this video: How To Replace a Fuse on a Furnace or AC Air Handler Control Board

4. Testing the Igniter

Confirm if the furnace’s igniter is cracked or faulty. 

However, some older furnace models have a pilot light instead of an igniter.

The pilot light/igniter ignites the gas coming from the burners. 


You should replace the igniter. Clean around the pilot light. If still not working, give the repair job to an HVAC technician.

5. Checking the Gas Supply

 A gas valve

Check to confirm if the gas supply is still on if using a gas furnace. If the gas valve is okay, confirm there are no leaks, which might result in your furnace not getting enough gas. 

However, don’t put on the carrier furnace if you smell gas leaking. 


Turn off the gas line if you notice a gas leak. 

6. Inspecting the Air Filter

When the carrier furnace air filter is clogged because of dirt, it experiences insufficient airflow. Restriction in the airflow causes the heat exchanger to overheat. 

You’ll notice a dusty layer buildup on the filters, or the furnace surface will appear gray. 


You should change the furnace filter. Ensure that the air vents are open and your home has proper ventilation. 

7. Cleaning the Flame Sensor

A furnace’s flame sensor detects if the burner has a flame. The flame sensor won’t detect flames if it is dirty or defective. 


You should use a fine abrasive pad to clean the flame sensor if it is dirty. Reach out to someone with experience for advice on cleaning the flame sensor to avoid further damaging it. 

Replace the flame sensor if faulty. 

8. Resetting the System

Most homeowners might not know that their furnaces have a rest button inside the blower compartment. The reset button automatically turns off the furnace if a problem occurs.

Most reset buttons are red or yellow. Though their positioning varies in various furnace units. But most are within the blower unit. Use the owner’s manual to locate the buttons. 


When you reset the system, most of the troubles will not happen frequently. It is necessary, especially if you’ve experienced a power outage. 

You can call someone with the expertise to help you reset if you’re unsure. However, if resetting still does not work, you should call a professional HVAC technician. 

9. Calling a Professional Technician

You may not know how to repair some of the abovementioned issues. Replacing a clogged filter may be way out of your league. Call a professional HVAC technician to help with answers to most of the questions you have. 

Some solutions to your carrier furnace not turning on might need replacing parts. An HVAC expert will evaluate the whole system and advise whether buying a new furnace is cheaper.

However, if you notice that you’re calling HVAC experts several times, we recommend buying a new furnace. 


  • Alanna Greene

    Alanna is an avid traveler who lives in Michigan. In addition to writing for Temperature Master, he also sells crafts on Etsy and takes long walks through the forests near her home.

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