Carrier Furnace Code 13 and Sometimes 33

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Many people take precautions to improve their in-home air quality. However, this can pose a challenge to ventilation and heating systems, since higher MERV-rated filters can restrict airflow. This, in turn, can put pressure on a furnace. When a carrier furnace gets insufficient airflow, it's likely to experience an "error 13" due to the automatic safety lockout.

In most cases, error 33 is a limit circuit fault. This means that the flame rollout switch or high limit impacts its operations. Consequently, you are likely to experience error code 13 than 33. Error 13 is a sign that the flame rollout or limit has been open for over three minutes.

If you want to fix this problem, you must ensure the furnace has the ideal airflow, and you should increase it whenever necessary. There are several troubleshooting tips you can perform on your furnace to fix the errors.

Ensure Proper Switch Operation

One way you can fix code 13 on your furnace is by checking for continuity in the high limit switch. However, for safety purposes, you should only do so after the furnace has cooled down. If you notice that the high switch limit is still open, then you have a faulty switch. Fix the switch or get a new one for effective use.

Besides, if the flame rollout switch is tripped, you should look for backdrafts to help keep it in good condition. You should also look for blocked flue and check the heat exchanger to determine the source of the flame rollout.

This is vital because it helps identify the problem in your furnace. It is also a good idea to reset the flame rollout switches by pressing the button behind its disc. However, it is vital to identify the model you are using because the settings vary.

man looking inside water heater device

Checking Airflow Issues

Checking whether there are airflow problems is also important. Ensure that the filter is not dirty because it can block airflow. If you are not sure how to evaluate the filter, seek the help of a professional.

This is essential because they can pinpoint the problem with the air filter. You should also open all vents and return registers where possible. Checking vents helps clear the air filter and prevent blockage.

Experts also advise that you clean the air conditioner evaporator coil. This coil is important in determining the performance of a furnace. When the evaporator coil is dirty, you are likely to experience error codes.

Checking the condition of the blower wheel is also important. Remember that some models use reverse blower wheels that need experience to operate. When examining the blower wheel, make sure it is clean, tight, and not missing any blades.

When there are insufficient blades, airflow will be affected, meaning the furnace will not perform efficiently.

You should also examine the blower capacitor and motor to ensure it is running up to speed. Failure to do so means you are likely to experience code 13. The furnace could also overheat and result in significant damage.

hands changing furnace air filter

Maintaining the Furnace

When a furnace is operating, moisture, dirt, and dust from condensation or humidity, and microbial growth can build up in the internal components. Various airborne elements from household surfaces and items can also result in formicary corrosion within your furnace.

If you don't service it regularly, these conditions can result in furnace code 13. In the worst-case scenario, there will be a total breakdown of equipment due to excessive temperatures.

With time, important components like the furnace heat exchanger, blowers, or burners can start corroding. This results in reduced performance of your furnace. The chances of experiencing error code 13 are also increased. The conditions might also result in leaking carbon monoxide.

A regular furnace tune-up yearly can contribute significantly to minimizing many of the issues discussed here. Given that most of these problems are caused by debris and dirt build-up, regular inspections help you detect any problems on the furnace.

Experts advise that you stick to regular maintenance checks to ensure that the furnace is in good condition at all times.

If you are not sure how to handle it, you should hire the services of a professional. Avoid handling the furnace if you don't have sufficient experience or knowledge.