Carrier Furnace Code 13 and 33 Reasons & Solutions

Carrier furnaces are a popular choice for home heating due to their reliability and efficiency. However, like all mechanical systems, they can sometimes experience issues that need to be addressed. One of the ways that homeowners can stay informed about their furnace’s health is by understanding error codes that may be displayed on the control panel.

Code 13 and 33 are two such codes that may be displayed on Carrier furnaces. Understanding these codes and their causes is an important part of properly maintaining and repairing your furnace. In this article, we will provide an overview of Carrier furnace code 13 and 33, including their definitions, causes, and troubleshooting tips.

You'll Learn About

What Are Carrier Furnace Codes 13 And 33?

Carrier furnace code 13 is a limit circuit lockout error, which means that the furnace has tripped its limit switch and will not reset until it has cooled down. This can be caused by a variety of issues, such as a clogged air filter, a blocked vent or flue, or a malfunctioning blower motor.

Carrier furnace code 33 is a limit circuit fault error, which means that the furnace is detecting a problem with the limit circuit. This can be caused by a variety of issues, such as a malfunctioning limit switch, a faulty control board, or a wiring issue.

These codes are usually displayed on the control panel of the furnace, either through a series of flashing lights or through an error code display. It is important to consult the manual or wiring diagram of your specific furnace model to determine how to interpret these codes and what actions to take.

Causes Of Carrier Furnace Codes 13 And 33

There are several common causes of Carrier furnace code 13 and 33.

There are several common causes of insufficient airflow through the heat exchanger, which can trigger a code 13 error on a Carrier furnace. Some of the most common causes include:

Plugged air filters: When the air filter in your furnace becomes clogged with dust and debris, it can restrict airflow through the furnace and cause the heat exchanger to overheat.
Blocked discharge vents: If the discharge vents that allow hot air to escape from the furnace are blocked or restricted, it can cause the furnace to overheat and trigger a code 13 error.

Obstructed air ducts: If the air ducts that distribute the heated air throughout your home are blocked or damaged, it can cause the furnace to work harder to heat your home, leading to overheating.
Dirty heat exchanger: A dirty heat exchanger can also restrict airflow and cause the furnace to overheat.
Failed blower motor: If the blower motor, which helps circulate heated air throughout your home, is not functioning properly, it can cause the furnace to overheat and trigger a code 13 error.

Malfunctioning Blower: The blower in the furnace is responsible for moving air through the unit and out into the ductwork. If the blower is not functioning properly, it can cause the furnace to overheat and trigger the limit circuit.
Malfunctioning Limit Switch: The limit switch is a safety feature that is designed to shut off the furnace if it overheats. If the limit switch is not functioning properly, it can cause the furnace to display code 13 and shut down.

It’s important to regularly maintain your furnace by checking and replacing the air filter, cleaning the heat exchanger, and inspecting the air ducts to prevent these issues from occurring. If you’re experiencing a code 13 error and are unsure of the cause, it’s best to call a professional HVAC technician for help.

Some of the possible causes of code 33 (limit circuit fault) include:

Malfunctioning limit switch: The limit switch is a safety device that is designed to shut off the furnace if it gets too hot. If the limit switch is malfunctioning, it can cause code 33 to be displayed.
Faulty control board: The control board is the “brain” of the furnace, and it is responsible for controlling all of the furnace’s functions. If the control board is faulty, it can cause code 33 to be displayed.

Wiring issue: If there is a problem with the wiring in the furnace, it can cause code 33 to be displayed. This could include loose or damaged wiring or incorrect wiring connections.

It is important to note that these are just some of the possible causes of codes 13 and 33. There could be other issues that may cause these codes to be displayed, so it is important to consult the manual or wiring diagram of your specific furnace model to determine the specific cause of the problem.

How To Troubleshoot Carrier Furnace Code 13 And 33

If your Carrier furnace is displaying code 13 or 33, there are several steps you can take to troubleshoot the issue. Here are some general guidelines to follow:

Consult The Manual Or Wiring Diagram Of Your Furnace

The first step in troubleshooting any furnace issue is to consult the manual or wiring diagram of your specific furnace model. This will help you understand what the codes mean and what actions to take.

Check The Air Filter

One of the most common causes of code 13 (limit circuit lockout) is a dirty or clogged air filter. Check the air filter and see if it needs to be cleaned or replaced.

Check The Vent And Flue

Make sure that the vent and flue that carry exhaust gases out of the home are not blocked or restricted. This can cause the furnace to overheat and trip the limit switch.

Check The Blower Motor

If the blower motor is not functioning properly, it can cause the furnace to overheat and trip the limit switch. Check to make sure that the blower motor is working properly.

Check The Limit Switch

If the limit switch is malfunctioning, it can cause code 33 (limit circuit fault) to be displayed. Check the limit switch and see if it needs to be replaced.

Check The Control Board

The control board is the “brain” of the furnace, and it is responsible for controlling all of the furnace’s functions. If the control board is faulty, it can cause code 33 to be displayed. Check the control board and see if it needs to be replaced.

Check The Wiring

If there is a problem with the wiring in the furnace, it can cause code 33 to be displayed. Check for loose or damaged wiring, and make sure that all of the wiring connections are correct.

If you are unable to resolve the issue on your own, it is recommended that you contact a professional HVAC technician for further assistance. A technician will be able to diagnose the problem and recommend the appropriate repairs.

Check The Furnace’s Slope

Make sure that the furnace is installed on a slope of about 1/8th of an inch from the back to the front of the unit. If the slope is not correct, it can cause condensate to build up in the secondary heat exchanger and restrict airflow, leading to a code 13 error.

Check The Furnace’s Ignition System

If the furnace’s ignition system is not functioning properly, it can cause the furnace to overheat and trigger a code 13 error. Have a professional HVAC technician inspect the ignition system and repair or replace it if necessary.

Check For Gas Leaks

A gas leak in the furnace can cause the furnace to overheat and trigger a code 13 error. If you suspect a gas leak, immediately turn off the gas supply to the furnace and call a professional HVAC technician for help.

How To Fix Carrier Furnace Code 13

If your Carrier furnace is displaying code 13, or limit circuit lockout, there are a few steps you can take to try and fix the problem:

Clean Or Replace The Air Filters

One of the most common causes of code 13 is a blocked air filter or vent. If your air filters are dirty or clogged, it can restrict the airflow through the furnace and cause it to overheat. To fix this issue, you can try cleaning the air filters or replacing them with new ones.

Clear Any Blockages From The Vents

If the air vents in your furnace are blocked or clogged, it can also restrict the airflow and cause the furnace to overheat. To fix this issue, you can try clearing any blockages from the vents using a vacuum or brush.

Replace The Limit Switch

If the limit switch is not functioning properly, it can cause the furnace to display code 13 and shut down. In this case, you may need to replace the limit switch in order to fix the problem.

If you are not comfortable attempting these repairs on your own, it is recommended that you call a professional HVAC technician to diagnose and repair your furnace. They will be able to identify the specific cause of the problem and make the necessary repairs to get your furnace up and running again.

Resetting The Carrier Furnace

If you have encountered error code 13 on your Carrier furnace, there are a few steps you can take to reset the system and try to resolve the issue. Here is how to reset your Carrier furnace:

Turn off the power to the furnace. This can typically be done by flipping the switch on the electrical panel that controls the furnace. Alternatively, you can unplug the furnace or turn off the circuit breaker that supplies power to it.
Once the power is off, wait a few minutes before turning it back on. This allows the furnace to reset and clear any errors that may be causing the issue.
Turn the power back on by flipping the switch on the electrical panel, plugging the furnace back in, or turning the circuit breaker back on.

Once the power is restored, the furnace will go through its normal start-up procedure. This may take a few minutes, during which time you may hear the furnace start up and then shut off again.
If the furnace is able to start up successfully, the error code should be cleared and the furnace should return to normal operation.
If the error code persists, or if the furnace is unable to start up at all, there may be a more serious issue that requires the attention of a professional HVAC technician.

More Tips

Here are a few additional tips for troubleshooting Carrier fault code 13 or any other furnace issues:

Check The Thermostat

If your furnace is not turning on or is not operating properly, it is possible that the problem could be with the thermostat. Check the thermostat to ensure that it is set to the correct temperature and that it is functioning properly.

Check The Furnace’s Electrical Connections

If you have checked the thermostat and all other visible components and the furnace is still not functioning properly, it is possible that there may be an issue with the electrical connections. Check the furnace’s wiring and connections to make sure that everything is secure and functioning properly.

Check The Furnace’s Fuel Source

If your furnace is not turning on or is not operating properly, it is possible that there could be an issue with the fuel source. If your furnace uses natural gas, check the gas valve and make sure that it is open. If your furnace uses oil, make sure that you have enough fuel in the tank.

Check The Furnace’s Safety Features

Many furnaces are equipped with safety features that will shut off the furnace if certain conditions are met. These features can include a high limit switch, a flame sensor, or a pressure switch. If any of these features are tripped, it could cause the furnace to shut down or malfunction. Check these features to make sure that they are functioning properly.

Follow The Manufacturer’s Instructions

If you are having trouble troubleshooting your furnace, it is always a good idea to consult the manufacturer’s instructions. These instructions should provide detailed information on how to troubleshoot and resolve common issues with your furnace.

More Things You Should Care For

When it comes to troubleshooting Carrier fault code 13 or any other furnace issue, there are a few things that you should know or have on hand to make the process easier:

Familiarize Yourself With The Furnace’s Manual

Before attempting to troubleshoot any issues with your furnace, it is important to familiarize yourself with the furnace’s manual. The manual should provide detailed information on how to properly maintain and troubleshoot your furnace, as well as safety guidelines and warnings.

Have The Right Tools

Depending on the issue, you may need certain tools to troubleshoot your furnace. These tools could include a screwdriver, a wrench, a flashlight, or other basic tools. Make sure that you have the right tools on hand before attempting to troubleshoot any issues.

Wear Proper Protective Gear

When working with furnaces, it is important to wear proper protective gear to help protect yourself from injury. This could include gloves, safety glasses, or a face mask.

Follow Safety Guidelines

Furnaces can be dangerous if not handled properly, so it is important to follow all safety guidelines and warnings when working with them. This could include turning off the power to the furnace before attempting any repairs, using proper protective gear, and seeking the help of a qualified HVAC technician if you are unsure or uncomfortable with the process.

Know When To Seek Help

If you are unable to troubleshoot the issue on your own or if you are unsure of how to proceed, it is always a good idea to seek the help of a qualified HVAC technician. A professional can diagnose the issue and provide the necessary repairs to ensure that your furnace is running safely and efficiently.

When To Call A Professional

There are several situations in which it may be necessary to call a professional HVAC technician for assistance with your Carrier furnace. Some of these situations include:

If You Are Unable To Determine The Cause Of The Issue

If you are unable to determine the cause of code 13 or 33 error, it is best to call a professional for assistance. A technician will have the knowledge and experience to diagnose the problem and recommend the appropriate repairs.

If You Are Unable To Safely Perform The Repairs

Furnace repairs can be complex and potentially dangerous, especially if you are not familiar with the inner workings of the furnace. If you are not comfortable or able to safely perform the repairs, it is best to call a professional.

If You Have An Older Furnace

If your furnace is older and has been experiencing frequent problems, it may be more cost-effective to call a professional for repairs. In some cases, an older furnace may need to be replaced rather than repaired, and a technician can help you determine the best course of action.

There are several benefits to hiring a professional for furnace repair and maintenance services. Some of these benefits include:

Expertise

A professional HVAC technician has the knowledge and experience to properly diagnose and repair your furnace. They will be able to identify the root cause of the problem and recommend the most effective solution.

Safety

As mentioned above, furnace repairs can be complex and potentially dangerous. A professional technician has the training and equipment to safely perform the repairs, ensuring that you and your home are protected.

Warranty Protection

Many furnace manufacturers offer warranties that cover the cost of repairs, but these warranties may be voided if the furnace is not properly maintained or repaired. By hiring a professional, you can ensure that your furnace is properly maintained and repaired, protecting your warranty in the process.

Overall, it is always a good idea to call a professional HVAC technician for assistance with furnace repairs and maintenance. They can provide the expertise and safety needed to properly maintain and repair your furnace, ensuring that it operates at its best for as long as possible.

Editor’s Note

Codes 13 and 33 are error codes that may be displayed on the control panel of your furnace. These codes indicate a problem with the furnace’s limit circuit.

Code 13 is a limit circuit lockout error, which means that the furnace has tripped its limit switch and will not reset until it has cooled down. This can be caused by a variety of issues, such as a clogged air filter, a blocked vent or flue, or a malfunctioning blower motor.

Code 33 is a limit circuit fault error, which means that the furnace is detecting a problem with the limit circuit. This can be caused by a variety of issues, such as a malfunctioning limit switch, a faulty control board, or a wiring issue.

To troubleshoot these issues, you will need to consult the furnace’s manual or wiring diagram to determine the cause of the problem. Some potential solutions may include cleaning or replacing the air filter, checking for blockages in the vent or flue, and checking for loose or damaged wiring.

If you are unable to resolve the issue on your own, it is recommended that you contact a professional HVAC technician for further assistance. Furnace code should be inspected properly.

Conclusion

In conclusion, understanding and addressing Carrier furnace code 13 and 33 is an important part of maintaining and repairing your furnace.

Code 13 (limit circuit lockout) and code 33 (limit circuit fault) are both indicators of problems with the furnace’s limit circuit, and addressing these issues is essential for keeping your furnace running smoothly. By following the steps outlined above and consulting a professional HVAC technician when necessary, you can effectively troubleshoot and resolve these issues.

Regular maintenance and troubleshooting can also help to prevent issues and extend the lifespan of your furnace. By taking care of your furnace, you can ensure that it provides reliable and efficient heating for your home.