[Fixed] AC Only Works When Driving and Blows Warm Air When I Stop 

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If you own a car, then you may already know how essential it is to have a fully functioning car conditioning system in your vehicle. There’s nothing else that can ruin a road trip quicker than a sweltering car interior, especially on a scorching hot summer day. 

However, the concern gets even more puzzling when your AC only works when driving and blows warm air when you stop, which can be very frustrating at times. There can be several reasons for such an issue to occur, such as low refrigerant levels, failing compressors, and more.

To find the right solution, you have to understand the root cause of the issue and prevent further complications. In this blog post, we’ll be diving deep into the possible causes behind the issue and provide practical solutions to get your car’s AC back in shape.  


Reasons Why Your AC is Only Working When Driving 

AC Condenser Blockage

If you experience that your vehicle is warm when stationary, but inspecting the fan shows no sign of malfunction, then there might be a problem with the condenser of your vehicle. It might be clogged due to dirt being accumulated with time. 

In that case, it’s a no-brainer that you would need to clean the parts and make the air circulate again freely. Also, make sure that you clean a clogged condenser as soon as possible otherwise it may get damaged even further. 

You should first start by inspecting the coil and then proceed to the condensers. Make sure that you clean them thoroughly and remove any dirt or debris formed on them. Doing this periodically can help you keep your vehicle’s AC in top shape for a long time. 

Low Coolant/Freon Level 

Freon is a coolant used for air conditioners that maintain an optimum temperature for your engine. Depending on the weather, the coolant will automatically adjust the engine temperature to keep it healthy and functioning. 

That being said, an insufficient level of this coolant may prevent your engine from maintaining a proper temperature as per the external environment. It may also reduce the efficiency of your system and you may observe these problems when the car is idle.

An easy way to determine insufficient coolant levels is by Noticing the clutch sound while starting the air conditioner. If it starts without any cloud sound, then it may indicate that your car is low on coolant as the clutch reads the coolant level before allowing the compressor to pressurize it. 

Moreover, since the components surrounding the condenser are more prone to wear and tear, any such issue may cause the coolant level to reduce considerably. If your car’s coolant levels are also decreasing gradually, make sure you check the condenser for any breakage.  

Worn Out Condenser Parts 

The condenser is also a critical component of an air conditioning system and requires proper functioning to ensure efficient operation. However, when this component becomes clogged, it may lead to a situation where your AC system may run at full capacity but will be ineffective.

As time goes by, several parts of the condenser such as the fan, motor, switch, and coil tend to wear out and reduce the capacity of the condenser. Fortunately, you can easily address this issue by cleaning the clogged parts and replacing the dead ones.  

Any issue with the switch or capacitors can be dealt with with ease. However, if your car’s condenser itself is clogged, it might be a bit more difficult to resolve and may even require you to replace the entire AC system in some cases. 

AC Condenser Fan 

The condenser fan is responsible to transfer heat from the indoor unit to the outdoor unit with the help of the condenser, which makes it crucial for the optimal performance of your car’s AC system, as without the fan, the system won’t be able to provide the required temperature. 

In case your vehicle isn’t moving, the lack of air circulation may make your AC system inefficient, which is where the condenser fan comes into play. Diagnosing any issues with the condenser fan requires you to check the fan wiring and connections to make sure they’re not loose. 

You should check the fuses or electrical relays to find out any electrical issues. If you don’t find any electrical issues but the fan still isn’t working, chances are that the fans are dead. This could indicate an issue with the thermostat switch or moto that prevents the fan from activating.  

Air Conditioner Compressor 

The compressor has often termed the heart of the air conditioning system of your car that works as a control center. If the system isn’t working efficiently, there can be several factors that might be responsible for it.

Some parts of the compressor, such as the cooling coil, may not be working properly due to faulty wiring. That’s also the reason why every auto repair technician begins by assessing the compressor when dealing with issues related to the AC.

One tell-tale sign of issues with your compressor is your air conditioner blowing hot air. Such an issue usually occurs when the system is out of the refrigerant required to work properly. It’s easy to identify the inefficiency when your car is stationary and there’s no airflow outside.


How Does a Car AC Work?

A car’s air conditioning system is quite similar to that of a home air conditioning system. They both utilize a similar set of components and refrigerants to provide you with cool air. However, the difference lies in terms of the refrigerant type and the power source used.

Your vehicle’s AC system is powered by the engine with the help of a drive belt when the car is running. It also powers several other electrical components such as the alternator, AC compressor, and headlights.

The compressor, as the name suggests, compresses the refrigerant and transforms it into a high-temperature and high-pressure gas. Then, the gas is transferred to the condenser removes the heat, and transforms the refrigerant into a liquid.

Afterward, the liquid travels through an expansion valve that drops its temperature and converts it again into gas. Then, it enters a receiver, a drier that removes the moisture, and lastly, it reaches the evaporator where a blower fan pulls air from outside and blows it through the evaporator core. 


Why Does Your Car AC Get Warm At Idle?

The reason your car’s A/C may become warm when idling is that the flow of refrigerant slows down, which affects its cooling ability. The cooling fan may also not be getting enough airflow when the vehicle is stationary, leading to the same issue.

Another possibility is a leak in the refrigerant system which can prevent the air conditioning from working effectively. It’s important to check for any blockages in the system, as well as for leaks, as these may prevent the air from being cooled and reaching the cabin. 


How Much Does It Cost to Fix AC Issues?

The cost of repairing your car’s A/C system varies depending on what’s wrong with it. Replacing the entire compressor can cost anywhere from $200 to $800, while a condenser fan replacement may cost between $300 to $500.

If the issue is more extensive, the repairs may cost thousands. However, these cases are rare. Smaller replacements such as hoses or sensors can cost less, around $300 if you find a good deal.


Final Words

So, as you can see, the problem of your AC only working when driving and blowing warm air when stopped can occur due to several reasons, such as inadequate cooling fan, slower refrigerant flow, clogging, and more.

Also, the cost of repairs varies widely on the root cause of the issue. Therefore, it is suggested to have your car inspected by a professional to identify the underlying issue and the required repairs. We hope this information proved to be helpful for you.


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