What to do when your AC only works when driving | Complete Troubleshooting Guide [2021]


What to do when your AC only works when driving

Are you wondering why your AC only works when driving? This article will evaluate the possible reasons why this might occur and how you can mitigate the discomfort. We understand that it can be pretty bothersome when your AC only works when driving. Thus, this prompted us to your our research. As a result, we made some beautiful discoveries that will be useful to you. 

Possible Reasons why your AC only works when driving:

  • Overheated engine your AC has broken condenser Fan
  • A clogged AC condenser
  • Depletion of Freon
  • Debris

If your AC only works when driving, it can be a dreadful experience in the hot summer when you have to make necessary pit stops that involve you waiting in the car. Do you want to know more? Continue reading to learn more about how each of these above-listed reasons may be why your AC only works when driving. We will also be providing resourceful answers to your pressing inquiries.

Why your AC only works when driving

Let’s get into more details…

When the electricity to an air conditioner is reduced, your car AC might display the earliest indications of trouble. This usually occurs while the car is at a standstill. The reduced cooling is not the result of a shutdown but instead of a capacity loss. 

The powerhouse of your AC can be divided into three major categories of parts that ensure the smooth running of your car’s air conditioner. They include:

  • AC condenser fan
  • Condenser 
  • AC compressor

The poor condition of any of the above-listed parts will result in a slight cooling effect and, in certain circumstances, a complete stop. These concepts and more are what we will be looking at in this section. 

1. Dealing with an Overheated engine

An overheated engine might be one of the reasons why your AC only works when driving. Most automobiles are equipped with two cooling fans, one for the condenser and the radiator. 

It’s no wonder that overheating engines are known to cause a slew of issues, one of which is decreased cooling. Because the engine isn’t functioning well, it can’t supply the necessary quantity of energy to the AC system. 

When the car is already hot, and the fans in the radiator and condenser aren’t operating as they should, the system won’t be able to cool it down as effectively

Heat is moved from the radiator to the condenser by the compressor in an air conditioning system. This, in turn, reduces the air conditioner’s ability to function correctly and results in a low cooling impact, significantly as the RPM declines.

2. Broken/faulty condenser Fan

The first thing you should check when figuring out why your AC only works when driving is the cooling fan in the condenser. If the fan is broken or unable to operate at total capacity, it will not cool the heat generated by the Freon, which passes through the condenser.

When the car is not moving, the motor fans are primarily relied upon to circulate the flow of Freon. The air conditioning system will not require a secondary cooler if the vehicle is moving. Because there is enough air flowing through the condenser while the car is running fast, the condenser does not need the fan to cool the Freon. However, while the automobile is not moving, the fan is the only way to cool the Freon.

What causes condenser fan failure?

There are various reasons to look into—a malfunctioning temperature switch, a bad coolant sensor, or a “stuck open” engine thermostat. As a chin effect, it never gets hot enough to trigger the fan. Those are the possible causes of fan failure. On the other hand, a broken fan control module and a faulty fan motor might be the source of all your problems.

What to do when your AC only works when driving
What to do when your AC only works when driving

How do I know if my condenser fan is broken?

You can keep an eye out for the following signs:

  • The cooling fans are not turning on.
  • When the air conditioner is turned on, the fan turns on, but the blades move slowly.
  • A rattling noise may be heard coming from the condenser unit.
  • It smells like something is on fire.
  • A fuse has blown.

Due to normal wear and tear, as well as the age of your condenser, fans might begin to fail. Dust accumulation, on the other hand, might obstruct its airflow, causing the engine to overheat. Makin periodic checks to see if the fan’s connections are loose is also very important. If it does not sit correctly in its slot, and if there is any damage that might limit its functioning. 

3. Clogged A/C Condenser 

The condenser is majorly in charge of keeping the air conditioner vents cool. It operates by converting Freon gases back to liquid. The condenser will not be able to process the Freon and create cold air if it has failed. When there is a power outage, such as when the car is idle, or the AC is operated solely on the battery, a damaged condenser may fail.

Condensers become clogged over time because of the accumulation of residue in the refrigerant. In most cases, this gradually develops into a sticky paste that obstructs heat transmission from the heated refrigerant to the cold ambient air pushed over the condenser coil.

What happens if AC condenser is clogged?

Short cycling can occur as a result of a clogged condenser. In most cases, you are causing the A/C unit to cycle on and off quickly and ineffectively rather than efficiently. Because irregular cycling causes additional wear and tear on all components, you may need to replace many parts at once or the entire A/C unit sooner than expected.

How do you unblock a condenser?

How do you clean a clogged car condenser? Well, it can be done in a few easy steps. First, when your condenser is clogged, to reduce or remove interference with the unit’s function, clean it thoroughly to get it back to its best. Second, to restore the condenser’s capacity, remove the debris from the coil. Because the coil is where the cold ambient air is pushed across, it is prone to accumulating dust and other impurities in the air over time. Check out this simple Youtube video tutorial on how to check your car condenser.

What causes condenser to fail?

Simply put, the coil, the motor, the fins, the condenser relay switch, the run capacitor, as well as tubes and seals, make up the condenser. If these parts become filthy or worn out over time, your condenser may stop working. 

  • Faulty condenser Motor
  • Condenser relay switch failure
  • A faulty run capacitor

4. Depletion of Freon

When your car or engine is idle, you may observe a comparable reduction in cooling; this, in most cases, is caused by a leak. This is because the compressor circulates Freon in the AC system to cool the cabin, and because of the amount of power it can take from the engine, it can do so best when the car is moving. 

Due to low power and low Freon, a stationary engine paired with a limited amount of Freon can cause the compressor to be unable to circulate enough refrigerant.

Can I Keep my car A/C with Low Refrigerant?

Your air conditioning system would be unable to chill your automobile if there was no refrigerant present. However, if your levels are low, you might be able to feel some cold air coming from your system. To remove heat from the air, air conditioners require refrigerant.

What causes low Freon in AC?

A leak in the AC condenser is one probable cause of low Freon levels. Normal wear and tear might cause the condenser seals and tubes to fracture or break. Another risk is that the condenser, positioned towards the front of a car, will be damaged by physical collision from road debris or rocks. Because the system relies on the refrigerant for functioning, a leak in the condenser might result in a low refrigerant charge and poor AC performance.

How do you know if your car’s AC is low on Freon?

  • Start your automobile, roll down all the windows, and turn on the air conditioning.
  • Allow a minimum of ten minutes for the engine to attain its ideal working levels while the engine is idled and the blower speed is set to 2.
  • Look for moisture in the AC pipe in the engine compartment and take note of the temperature. The pipe should be chilly to the touch, with condensed water visible above it.
  • Examine the same pipe close to the firewall. If you find that it’s colder, the gas volume may be below.

5. Debris/Dust accumulation

Because automobile air conditioners are placed in the vehicle’s front, contamination or debris entering the system is typical. The material might obstruct the condenser or ruin the cooling fans, which are two significant issues. 

Foreign object-related problems can have various negative consequences for the system and should be handled by professionals with a thorough examination. 

If you find yourself idling without appropriate cooling after a very windy day, your air conditioning system may be damaged. For example, a blown fuse or damaged fans produced by the debris hit might cause a cooling halt while the vehicle is idle.

What to do when your AC only works when driving
What to do when your AC only works when driving

AC only works when driving: Conclusion.

It knows why your AC only works when driving can save you a great deal of trouble and cost, allowing you to address the right issue directly. However, it’s sometimes necessary to pay attention to minor details to get to the root of a problem. This is why we are committed to providing you with updated information on subject matters that interest you.

A good vehicle service should be enough to get your AC back up and running. This concludes our research on why your AC only works when driving. However, there is still value to gain. If you’re having trouble figuring out an issue or have questions about auto AC and idling, please let us know in the comments.


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