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AC Only Works When Driving

AC Only Works When Driving: Causes & Fix

The air conditioning system inside the car has the great benefit of keeping the temperature around us always at the most appropriate level, no matter how harsh the weather outside. So if this part does not work smoothly, it will make using your car much more difficult.

Among the problems with A/C, we found that the system only works when moving is the error that users have the highest rate of encounter. So what is the leading cause for this problem?

About Air Conditioning System

AC Only Works When Driving

Before conducting an analysis of the main causes of air conditioning not working when stopping, we will need to know a few things about the structure and how the air conditioner works.

Basically, the air conditioning system installed in the car also helps us balance the ambient temperature in the same way as the air conditioner in the house. Both try to push out the latent heat inside the body by converting them to a vapor state with Low-pressure cold air.

Although they are just invisible gas lines to our eyes, to create enough cold air is a complex operation of many different details in the air conditioning system. First, the air flows will be available by compressing the refrigerant inside the car’s air conditioning unit.

After that, this gas will continue to flow through the condenser and turn into a liquid with high pressure. Inside this unit, impurities and moisture molecules will be completely removed, ready to flow into the throttle or orifice.

Finally, they are depressurized to lower the temperature and the physical state back to the original gaseous state.

Reasons Why AC Only Works When Driving

Why AC Only Works When Driving

We can see that the operation of the air conditioning system is not simple at all when it has to go through a large number of stages in many different parts.

Moreover, the fault diagnosis will become even more difficult because the details are scattered all over the vehicle. However, there are still some locations where the damage of the air conditioning system will often appear, such as:

Hydraulic problems under the hood

Common faults in this location just under the hood will typically be refrigerant-related such as a lack or excess of refrigerant in the required amount or a malfunctioning refrigerant delivery control function. In addition, compression damage is also concentrated in this area.

Electric problems under the hood

The electrical system under the hood plays an essential role in the adjustment to ensure the smooth operation of the air conditioner. But this is also one of the most problematic locations, particularly with electrical equipment such as clutch coils and relays, high-pressure trip switches, low-pressure trip switches.

Electrical problems in the dash

The control panel will help you quickly adjust the operation of the cooling system to your liking.

So sometimes failures in this location can give false information and make the air conditioner less stable.

Problems in this location are usually related to a damaged switch, control head, or intelligent module.

Mechanical problems in the dash

The mixing door is broken, or the mode door is damaged, causing air to not pass through the vents. Even the recirculation door is damaged, and falling on the blower motor is usually the leading cause of damage to the outlet of the indoor unit.

Among the many problems that cause the air conditioner not to work when stopping the car, 5 issues are most likely to appear, and worse, all of them are not concentrated in one but dispersed in different locations.

You should also note that these failures can occur both alternately and at the same time.

Low refrigerant levels

More air flows through the condenser when the vehicle is running, which helps the air conditioner work more efficiently and use less refrigerant. Conversely, when the car is stopped, the system will start using a more significant amount of refrigerant than usual.

And if the solvent responsible for this critical job is in short supply, the subsequent cycles will immediately stop leading to the air conditioner stops.

Often this situation will happen when you do not maintain the vehicle regularly, leading to shortage or leakage of refrigerant. Also, if there is a problem with the pipes, the chemicals will not move properly.

Bad or Failing Fan Clutch

Fan Clutch plays a significant role in ensuring that the A/C stays on even when the car stops and no air flows through the condenser. Because the car’s temperature control system will use this built-in fan to circulate the flow of refrigerant when the car stops.

Thereby it helps the solvent to complete its transformation cycle. Because of this, damage to the secondary cooler, such as breakage or chipping, will prevent refrigerants from moving and disrupt the whole system.


A piece of debris and impeding the circulation of coolant can also cause damage to delicate components. The most common of which is the rotor phenomenon and the filter being broken due to impact with debris when operating at high speed.

Overheating Engine

Engine overheating is also one of the causes of the air conditioner stopping when we stop the car. Because if not in the best state, the engine cannot provide enough power for the air conditioning system to operate continuously.

Frequently Asked Questions

How much does it cost to fix this error?

It will cost you about 200 to 800 dollars to repair the fault inside the car’s air conditioning system. The above cost may vary depending on the type of vehicle you own.

Is it possible to repair it yourself at home?

You can do simple tasks like adding coolant at home, but we still recommend leaving processes like testing and repair to skilled artisans.


Above are the problems that can be the leading cause of the air conditioning not working when your car stops. We can see that the result is just discomfort, no matter how big or small the damage is. So pay attention to every small change as well as maintain the car regularly.

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