The uncomfortable ride of the malfunctioning AC causes a lot of annoyances. One of the most noticeable issues is that the car AC turns on and off randomly.
This problem makes us hard to enjoy every journey and damages the entire air conditioning system. To get in-depth into the reasons, we shall walk you through how it works and the most common causes.
Let’s get started!
How Does A Car’s Air Conditioning System Work?
To understand how a car’s air conditioning system works easily, we will give you two methods to explain.
One way is brief, and the other method is through understanding how the main components manipulate.
Brief Understanding Way
In an easy-to-understand way, through temperature changes and the preset pressure composed of 5 components in the car’s air conditioning system, it transmits the refrigerant in the form of liquid to the gaseous state.
It absorbs the heat and humidity from the vehicle inside and then gives off the cool, dry air.
A Deep Understanding Way
A deeper understanding comes from how the main five parts operate through the high and low-pressure stages.
Through this analysis, you can understand why the car AC turns on and off randomly. Now, let us walk you through the main points.
Under the high-pressure side, the refrigerant in a gaseous state is drawn into the compressor. The compressor acts as a pump driven by the belt, connecting to the engine’s crankshaft.
The refrigeration gas is forced into the condenser. The cooling coils and fins of the condenser release the heat from the circulating refrigerant.
The refrigerant continues flowing through the tiny tank called the receiver or dryer. At this stage, desiccants in the dryer remove water from the refrigerant.
The change from the high-pressure side to the low-pressure side occurs in the thermal expansion valve.
The expansion of the refrigerant reduces pressure and then transfers the low-pressure liquid refrigerant to the evaporator.
In the evaporator, a magic process happens, which boils refrigerant by the car’s heat inside. It returns to the original gaseous state and moves out of the evaporator to enter the cabin car.
Now, it absorbs the air’s heat and leaves the cooler air behind. The fans will blow the cool air into the cabin. The refrigerant enters the compressor and then is compressed to restart the whole process.
Top 8 Common Reasons Why Your Car Ac Turns On And Off Randomly
Understanding how a car’s airconditioning system work makes it easy for you to answer the most frequently asked question why my car ac turns on and off frequently.
Among multiple reasons, the top 8 following reasons are the primary factors leading to this issue. Let’s check it out.
Short Cycling
Short cycling is the most noticeable phenomenon, which keeps ac cutting on and off in car. Under normal conditions, the car AC compressor stays on until the car compartment reaches the set temperature on the thermostat.
A cycle lasts approximately 15-20 minutes before the AC compressor switches off. It restarts the pattern once the cabin temperature increases.
The compressor shortens the cooling cycle when it stops prematurely—being stuck in the start-up cycle or the continuous repetition of the on/off cycle results in significant wear to the car AC.
Some main reasons cause to the short cycling coming from:
- A dirty air filter
- An improperly sized air conditioner
- Refrigerant leaks or improper refrigerant charge
- A faulty thermostat
- Air escaping through a leaky ventilation system
The Build-Up Of Dirt On The Compressor Or Condenser
A clogged condenser is another reason. The build-up of debris, the remain of high-pressure liquid refrigerants, or grime makes the air conditioner struggle, overheat, then shut off randomly.
Besides making the AC turn on and off in car wrongly, the dirty condenser coils affect the further stages.
As we explained above, the condenser converts the high-pressure refrigerant into liquid form and then cools it before the conversion process occurs.
Once the condenser is clogged with debris, it is impossible to dissipate the heat.
Dirty Cabin Air Filter
The dirty air filter is the most common cause of every air conditioner’s issue. If you forget to replace the new filter or find more dust accumulation on furniture surfaces near the vent, it is time to change the new filter.
As a result, the air filter is the first thing you should check once you notice the AC unit’s failures. The clogged air filter is usually the foremost cause, which AC goes in and out sporadically.
The grime buildup on the air filter reduces the airflows into the AC unit. Sequentially, it leads the coils to freeze up. This way, the air conditioner suddenly turns off without completing a cooling cycle.
A few minutes later, you will notice that the thermostat will switch the AC on again. Then, it repeats to turn on and off randomly.
Cleaning the air filter is the easiest way to prevent suffering from this problem. This process is pretty easy, but you can take your car to a repair shop and let a mechanic have an overall check for your vehicle if you don’t have time.
Refrigerant Leak
Freon works as a substance or a non-flammable gas in the air conditioner. It participates in the evaporation process.
Undoubtedly, any refrigerant leak or insufficient freon level affects the AC’s constantly switching on and off.
The noticeable sign of freon leak is the thin greasy substance appearing under the vehicle, inside the cabin, or under the hood around the compressor. You may also hear the hissing sounds from the cooling system.
This mechanical problem forms the frost layer on the evaporator coils. Like the dirty cabin air filter, it leads to short cycling.
Dirty Evaporator
Among multiple issues caused to the AC going in and out in car, the cooling system freezing up stays top of the main reason.
The blocked evaporator is a major malfunction to repeatedly keep the AC cutting on and off in the car.
Let’s look for water under your vehicle, which may hint at a freezing problem.
Compressor Failure
As mentioned before, the compressor participates in building pressure and transferring the freon continuously. As the heart of the car air conditioning system, its failures stop it from working properly.
Once the compressor goes wrong, it can’t supply sufficient cooling power for your system. As a result, the car AC turns on and off by itself.
Long time no usage is the primary factor that leads to the defective compressor. Without the movement of the pump driven by the belt, components tend to stick together and function imperfectly.
Having it frequently started up is the best method of protecting the air conditioner. Let’s run it at least 15 minutes every three weeks to keep every part operating smoothly.
In other circumstances, even the new compressor replacement can’t make the AC unit work properly again. It comes from the lack of lubrication, a production fault, or a metal chip.
If the problem comes from the metal chip, there is no other choice other than to replace the entire air conditioning.
Bad Blower Motor
Intermittent cooling also often occurs due to faulty cooling fans. The low airflow or no air forces the blowers to work harder to cool the car’s compartment down.
Over time, a faulty blower motor can only emit hot air. It will lead to the overheating air conditioner. Finally, the car AC cuts on and off automatically.
Another recognizable sign of the bad blower motor is abnormal sounds in operation.
The errors of blower motos come from an electrical issue. Cracks in the blower fan, electrical connections, and blown fuses are among the major problems.
In such a situation, replacing the new part is necessary to avoid AC cutting on and off in the car.
Faulty Blend Door Actuator
The blend door actuator is in charge of controlling the car’s climate control system. When you turn the dial to adjust the temperature of airflows, the signals are sent to the blend door actuator.
Despite checking various AC components, you still can’t understand why does my car AC go in and out? The problem could possibly come from the faulty blend door actuator.
The most typical symptoms of a faulty blend door actuator you could recognize through:
- Knocking sound: This sound is quickly noticeable once you start the car or AC unit.
- A clicking sound: The constant and repetitive clicking sound is also easy to detect. It usually comes from the HVAC control’s placement on the dashboard,
- Strange noise: You may also experience strange noises such as droning or squeaking sounds. It tends to get louder once you adjust the temperature or turn the AC on.
- Inconsistent temperature: The sudden temperature changes between hot and cold without your adjustment.
Conclusion
In short, this comprehensive post can analyze the major causes of “car AC turns on and off randomly”.
Thus, we can easily conclude that the dust accumulation on the main components is the most significant problem.
Maintaining and thoroughly checking the cooling system at least once per year is vital to avoiding squeaking or thumping noises, expanding its lifespan, and enhancing ride comfort.