Imagine enjoying your days with the fresh, breezy air blown from your beloved car on a sunny day. Then, one day, you suddenly realize that your air conditioner’s air only blows through the defrost vents while the others stop working. Even when you restart the engine, everything still works the wrong way and causes you a lot of confusion.
So, to help you solve this problem, we will now address the issue for you in the quickest way and share some of the most effective solutions for handling your defrost vent to ensure a cool and safe journey.
Air Only Blows Through the Defrost Vents: The Malfunction Is the Problem
Generally, we can solve any issues related to the car’s ventilation system fairly quickly because it’s not a complicated problem. Due to high pressure, the air surrounding the car will be drawn into a duct at the front and some small ones along the grille above the hood when the car moves at high speed. The external air flows, at the vehicle’s intake, will be heated or cooled by the air conditioner, then distributed throughout the interior via air ducts scattered inside the cabin. Ultimately, these air waves will then pass through a vent at the rear to exit, completing a smooth ventilation cycle inside the car’s cabin.
Nowadays, some vehicles are also equipped with a different ventilation system, where the air recirculates inside the vehicle’s cabin without being blown out. The vents will draw in the air while reheating or cooling it again, then send it back into the car. This defined system setup is beneficial if you don’t want hot, humid, or foul-smelling air to infiltrate your car while keeping the air inside the cabin fresh and cool.
In seasons with extreme weather conditions like summer or winter, as we often turn on the air conditioner to keep warm or cool down while traveling on the road, the ventilation system, especially the vents, may have to operate continuously and lead to overuse. Like almost everything, after a long period of use and poor maintenance, they can get clogged, develop bad odors, deteriorate, and even damage surrounding automatic parts, whether related or not.
Not only does the AC blow through the defrost vents, but anything that interferes with the smoothness of the ventilation system while you’re on the road should be noticed and requires intervention to be fixed promptly before it can cause many other uncontrollable damages.
How to Fix AC Stuck on Defrost
Who would want to sit in a car filled with awkward condensation on the windows and that smells bad? You probably also don’t want your beloved air conditioner to break down in the middle of a hot summer or cold winter.
Defrosting is a vital function that can prevent your vehicle from freezing and frosting over during cold winters. Moreover, not only is it a part of the ventilation system working hard to do its job, but the defroster plays a significant role as it can affect the smooth operation of the temperature control system and the safety and health of the vehicle, as well as the driver.
Finding the cause and solution for stubborn stuck defrost vents in advance can save you a trip to the garage for a full repair and cleaning process. Although the cost of cleaning and repairing a car with a ventilation system issue isn’t too expensive, it will waste a lot of time and effort that isn’t worth it.
That said, take a closer look at the following causes and solutions for this rather bothersome car defrost stuck issue right now.
1. Mode Door Actuator in Bad Condition
The first cause of AC only blowing through the defrost vents problem is a faulty mode door actuator. The function of the mode door actuator is to control the vents to ensure that air is blown correctly according to custom settings.
Nowadays, many modern door actuator systems have been gradually developed based on automation. As you can see, even modern systems that integrate multiple types of high-performance technologies will wear out and fail over time, not to mention manual systems. The actuator is also always in a vulnerable phase because it’s often exposed to air from various raw air sources.
It’s a device equipped with plastic gears that can easily break and slip during operation. Additionally, the door actuator can encounter many problems and operate incorrectly due to overload, incorrect or confusing wiring, poor quality of incoming air, and even improper installation.
One of the most visible signs indicating a mode actuator problem is that when you turn on the air conditioner, the front vent slot makes a clicking sound, and that’s when the air only blows through the defrost vents issue occurs. And the next notable thing is that you need to find a way to fix this problem. When the mode door has difficulty functioning correctly, you should unplug it immediately and rotate it inside with your fingers.
If your rotation feels smooth and there doesn’t seem to be any difficulty running, you can be relieved with that. Remember to clean your car’s mode door actuator from time to time to ensure it will function correctly and efficiently during a season with extreme weather conditions if unfortunately encountered.
2. Obstructed Air Intake
Normally, air enters the car in two main ways: the first is the vents above the dashboard, and the second is the duct where air is recirculated in the car. If both of the above air blowing lines are blocked or obstructed by obstacles, the vehicle will face an AC stuck on defrost problem, where the air will be concentrated in one vent without being able to escape.
Obstructed air intakes are mainly caused by obstacles falling into the vents while you’re traveling on the road, such as nuts, dead leaves, long sharp sticks, or bird nest branches. All these direct factors mentioned above cause blocked vents that you need to address immediately to avoid long-term consequences that are difficult to resolve. A dirty ventilation system will affect the air quality and temperature every time you travel. And no matter how cool the destination may seem, the polluted air in the car always gives you a not-so-great experience.
To solve this problem, you should clean and possibly replace the air filters without spending too much time analyzing why the air only blows through the defrost vents.
You can completely pump pure air to filter out pollutants that cause health issues. Moreover, all the home solutions you can think of for cleaning the air intakes are highly recommended to save money, instead of going to the repair shop, as long as they don’t damage or break the system.
Try to ensure you clean the air intake at least once a week with specialized cleaning solutions from supermarkets. Although they are just simple small actions, they will be effective in the long run.
3. Broken Blower Motor
The function of this part is to blow air through the vent. It can also check the amount of air blown when combined with a blower motor resistor. With such irreplaceable functions, a damaged blower motor will cause serious problems for your car. A vehicle operating with a damaged blower motor cannot expel air through the vents, resulting in no airflow to regulate and balance the air inside the cabin.
The most common problems with the blower motor are corrosion and tearing. As it fails, you can easily spot the issue by the loud humming when you start the air conditioning system, or you’ll hear an unusual vibration. If you have to travel for a long time and your car runs longer than usual, you might smell a burning odor from the vents due to overload and overheating.
And gradually, starting from a seemingly tiny part, every component of your motor will deteriorate if it often faces air restriction issues, the most notable causes being rust and overheating.
The best way to care for a damaged blower motor is to identify the causes and address the problems. If you don’t want the car’s components to suffer from overheating due to air restriction, pay close attention and take good care of the ducts. You should also watch out for rust issues, preventing dirt from entering your blower motor. Quickly repair any leaks in the blower motor if you notice strange smells or noises and change the air filter periodically.
4. Faulty Blower Resistor
The blower resistor will blow cold or warm air through the vents when you turn on the AC/heater and set the car’s fan to operate at various speeds according to your needs. When the car’s air conditioner is stuck on the defrost vents, your blower resistor might be faulty and requires intermediate repair.
Thermal overload or overheating is the main cause of this problem. So, to give the blower resistor full control over the airflow and strengthen the cabin air, have it replaced at a professional repair shop.
5. Damaged Blend Door Actuator
The function of a blend door actuator is to regulate and control the temperature in the car by allowing or preventing air from passing through the heater core. This part is made of plastic gears, which are quite fragile and unstable. Being made from non-rigid materials will create more opportunities for the blend door actuator to be exposed exclusively to damaged and broken conditions. Not only that, but this part is also prone to operating erratically or even ceasing to function when the electric motor is in an exhausted state caused by excessive and prolonged operations.
Keep an eye on the temperature in your car whenever you turn on the air conditioner. If you feel the temperature gradually becomes erratic or doesn’t cool and heat effectively as you customized the system, your blend door actuator is very likely to have issues that require immediate repair. Before the actuator is completely damaged and cannot be repaired with regular cleaning and maintenance methods, you can easily hear small ticking noises coming from the dashboard.
Considering the problems deemed quite serious with this type of actuator, trying to fix it temporarily is not a good idea. However, you can still replace the broken one with a brand new one with just some disassembly and basic tools. If you’re not confident in your mechanical skills, find a reputable repair center to ensure the system returns to proper operation as soon as possible.
6. Blown Fuse in the Ventilation System
The annoyance of seeing air blows only through the defrost vents of the car can also be triggered by a blown fuse, the part that protects the entire ventilation system from dangerous sudden voltage surges (electrical surges). When this unpleasant phenomenon occurs due to a short circuit, electricity won’t be able to reach the blower motor, so the ventilation system may stop working.
There are 3 types of fuses you need to pay attention to if you encounter the above situation. These are the ventilation fuses, the blower fuses, and the AC compressor magnetic clutch fuse. Generally, fuses have the effect of protecting the windings that connect the entire electrical circuit or limiting cases of serious explosions in your vehicle’s system.
You should pay attention to regularly monitor and check the car’s fuses. If they blow again even after replacing them previously, take your vehicle to the nearest repair shop for a comprehensive consultation and examination.
7. Bad Relay (Electrical Problem)
The relay must supply current to the blower motor for it to operate. If this doesn’t happen, the ventilation system will be limited, forcing the air to pass only through the defrost vents.
Due to the continuous actions of opening and closing, the relay is tolerant to wear and tear. And it’s also one of the reasons why the blower cannot function properly to ensure the car’s ventilation system encounters no obstacles. Another sign of a faulty relay is if you feel hot or warm when you touch it, indicating that the relay has absorbed too much heat as a result of the failure.
Check and replace the relay periodically if you don’t want its problems to add more complications to the entire ventilation system and air quality whenever you get into your vehicle.
Wrap Up
Here are some of the main causes and solutions for the problem of car air conditioner air blowing only through the defrost vents that we would like to introduce to you today. With the article above, we hope you better understand the importance of vehicle ventilation systems as well as vents for better air quality and good health.
No one wants to get into a stuffy, secretive, and foul-smelling car. So, remember to identify the cause and address it appropriately to avoid wasting precious time on fruitless efforts. Take good care of the ventilation system, air conditioner, and all components of your vehicle that contribute to a pleasant and cool drive. You might be surprised at what a small act of maintenance can do for a car composed of a thousand parts.