How To Reset A Carrier Furnace

If you’re experiencing issues with your Carrier furnace, it is a good idea to reset it first and see if this would revert the system to normal. Issues like ignition lockout are usually resolved by resetting the Carrier furnace. We’ve consulted multiple resources to get the exact steps to reset a Carrier furnace for you.

Follow these simple steps to reset your Carrier furnace:

  1. Locate your thermostat and turn it down to prevent it from triggering the need for heat from the furnace.
  2. Turn off the breaker switch that supplies power to your furnace, or you can unplug the furnace.
  3. Wait for 30 seconds.
  4. Turn the breaker switch back on or plug your furnace back in.
  5. Turn up your thermostat.

Although the steps to reset your Carrier furnace can be simple to follow, there are important safety precautions that you need to know to ensure that you do not get injured while troubleshooting your Carrier furnace. Additionally, there are common issues below that you check in case resetting your Carrier furnace did not resolve your issue.

A professional technician checking house heating unit, How To Reset A Carrier Furnace

Safety First

Troubleshooting or repairing a furnace can be a dangerous activity if safety precautions are not properly followed. Performing repairs while the Carrier furnace is still connected to electrical and gas supplies can result in serious injuries, property damage, or even death.

Look for the circuit breaker switch in your Carrier furnace and flip the switch to the “off” position to prevent unwanted electrical current from getting into the furnace during troubleshooting.

Next, look for the gas supply valve and turn this to the “off” or “closed” position to disrupt the gas supply. Turn the electricity and gas back on only when you are done with the repairs and troubleshooting.

What causes a flame rollout switch to trip?

Whenever the flames reach areas of the furnace where they should not go, the temperature inside the furnace will start to rise. Flame rollout switches are sensitive to changes in temperature inside the furnace cabinet.

It detects unusually high temperatures around the burners and will get tripped if these temperatures get too high. As a safety precaution, the furnace will stop burning once this switch is tripped.

If your furnace keeps turning off after a certain period, this could be the culprit. There are several possible causes behind this issue.

Clogged Exhaust Vent

If the exhaust vent is clogged, the airflow will be limited. Limited airflow can cause the flames to escape.

Clogged exhaust vents can be caused by bird’s nests, soot buildup, or tree branches and leaves. Check out this article for cleaning furnace vents in seven easy steps.

Clogged Heat Exchanger

A similar situation will occur if the heat exchanger is clogged because the flow of air will be restricted. Flame rollout can also happen in this situation.

Heat exchanger clogging is often caused by corrosion or soot buildup. Soot comes from gas molecules that do not combust completely. Over time, this can form and accumulate inside. A small amount is normal for any furnace. However, too much soot buildup could become an issue for the furnace.

A clogged heat exchanger makes your furnace inefficient. It can even prevent your furnace from functioning at all. It is recommended to hire professional HVAC personnel to clean the heat exchanger.

Cracked Heat Exchanger

A cracked heat exchanger becomes ineffective because it loses the ability to create sufficient pressure. This causes flame rollout.

Another sign of a possible cracked heat exchanger is when your carbon monoxide alarm keeps going off. A damaged heat exchanger can cause combustion gases to escape and seep into the rest of your house.

This is dangerous because combustion gases like carbon monoxide are toxic. A professional should verify the possibility of a cracked heat exchanger as soon as possible due to the serious health risks involved.

Low Gas Pressure

Pressure gauge with a neddle dial

Low gas pressure can also cause flame rollout. A low gas pressure causes the flames in the furnace to roll out instead of going into the heat exchanger. This is usually caused by dirty burners. When the burners get clogged, the gas pressure will drop because the passageway of the gas is not enough to produce the right amount of gas pressure.

What to do when a furnace is not heating?

The reasons below are among the most common why a furnace is not heating.

Flame Igniter

A faulty flame igniter can prevent a furnace from heating. A cracked igniter can prevent it from generating the required amount of heat to ignite the gases inside the furnace.

Moreover, if there is no continuous electrical flow through the igniter, then it could prevent the furnace gases from igniting as well. Replacing the igniter will solve this issue.

Click here to find this replacement flame igniter from Amazon.

Flame Sensor

Flame sensors detect if the furnace successfully ignited. If it doesn’t detect a fire, the control board will prevent electricity from flowing through the gas valve and prevent it from igniting.

A dirty sensor might no longer be able to detect combustion. This can be cleaned with nylon cleaning pads. If it fails to sense fire after cleaning, it will have to be replaced.

Check this article for other reasons why a furnace keeps shutting off.

Click here to find this replacement flame sensor from Amazon.

Draft Inducer Motor

This motor sucks air for the heat exchanger. A switch that is sensitive to changes in air pressure watches out for any changes. It will close another switch that tells the control board of sufficient airflow if there is enough change in the pressure.

A defective draft inducer motor can fail to trigger the pressure switch, and this will cause the ignition process to fail. Once this happens, the furnace will shut off automatically in a few minutes. Have a professional replace a faulty draft inducer motor.

Control Board

Heater circuit control board inside of furnace

Control boards regulate the electrical supply for the different components of a furnace. If the control board fails, the ignition system will not receive power for the furnace to produce heat. A defective control board needs to be replaced.

Wall Thermostat

The wall thermostat controls the temperature of a heating system and sends power when more heat is needed. If the electrical contact in the thermostat is defective, the furnace will not receive the electricity it needs to turn on.

Test the thermostat’s electrical continuity with a multimeter. Replace the thermostat if it doesn’t have electrical continuity anymore.

Gas Valve

Officer turning valve on gas bottle

The gas valve regulates the flow of gas. A defective gas valve could fail to open and provide the furnace with the sufficient gas supply that it needs to produce heat.

To test the gas valve, use a multimeter and check for circuit continuity. Have a professional replace the gas valve if needed.

What do blinking lights on your Carrier furnace mean?

The blinking red lights on the Carrier furnace are codes made up from a series of long and short flashes. Identifying the pattern from the blinking red lights can tell you the code that represents an error message.

Each code represents a status based on the number of short and long flashes. Consult the user manual of your Carrier furnace to get the meaning of each code and advice on what to do.

If you can’t find the manual, there is usually a sticker inside the cabinet cover of your Carrier furnace. This sticker contains a summarized table of codes and what they mean.

How to test a flame rollout switch?

If you suspect a faulty rollout switch, you can test it using the following simple steps.

The flame rollout switch is a safety device that protects the furnace from flames rolling out by detecting a spike in temperature around the area of the burners. If flames roll out, the surrounding temperature will start to climb, and the rollout switch will open to stop the flow of gas to the burners. This prevents damage to your furnace due to uncontrolled flames rolling out.

To test the flame rollout switch, you’ll need a temperature meter with a probe. Hold the thermometer probe near the rollout switch. The probe should detect a similar temperature as the rollout switch. This temperature should be close to room temperature if your furnace is not having any flame rollout.

If the temperature starts to climb rapidly, that could mean a restricted airflow or vent or high gas pressure.

If the display on the temperature meter gets very high, but the rollout switch did not trip, then the rollout switch could be defective. On the other hand, if the temperature on the meter is close to room temperature but the rollout switch trips, then the rollout switch is defective and needs to be replaced.


Resetting the Carrier furnace is a common first step for troubleshooting common issues like an ignition lockout. Always remember to follow safety procedures when troubleshooting or performing repairs on your furnace.

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