Causes of Car Ac Only Works When Accelerating

If car ac only works when accelerating, you have a faulty AC system. The AC is meant to work as soon as it is switched on.

The problem of AC only working when accelerating has led us to treat some related topics to this issue in this article. As you read on, you will understand its causes, fixes, and how much it costs to fix.

ac only works when accelerating

Car Ac Only Works When Accelerating

It is not normal when your ac only works when driving. It is a sign that there is something wrong with parts of the vehicle related to the cooling or AC system.     

There are a lot of failing parts of a vehicle that could affect the way the AC works.

To better understand how what could cause your ac only work when accelerating, you need to know how the system works.

When you start your vehicle, the engine powers a drive belt by continuously rotating it. In turn, the belt powers a large part of the electrical system in the car, including the alternator and AC compressor.

The compressor compresses the refrigerant, which is converted into high-pressure gas and then transferred to the condenser. In the condenser, the gas is transferred to liquid which is then pushed to the expansion valve.

Once the gas is in the expansion gas, the liquid refrigerant is converted to its original gas form, and then the temperature drops. It then flows to the receiver or drier; in this place, the refrigerant is dried, and all moisture is removed.

In the final stage, the refrigerant is transferred to the evaporator and blown through the evaporator core with the help of a blowing fan. It then moves beyond the core and circulates through the car vent.

Now that you understand how your AC works, note the components involved. If any of them is faulty, it could lead to poor AC system functioning.

Possible Causes of ac only blows cold when driving

Many components could cause your ac not to work when idle. They include the following.

1. Low refrigerant level

The AC system depends a lot on a specific type of fluid called the refrigerant. A common cause of problems like ac working sometimesor only working when their vehicle is accelerating could be due to low refrigerant.

The fluid is what cools the air coming out from the AC vent. All you will get is warm air when it is low or finished. 

2. Faulty condenser fan

The most common cause of ac only blowing cold at high rpm and warm at lower rpm is a bad condenser fan or loose belt. The function of the condenser fan is to remove heat from the condenser and reduce the refrigerant’s temperature.

A condenser fan will come on when the engine reaches operating temperature. If the fan does not come on, the refrigerant does not change in temperature when transferred to the evaporator.   

3. Engine Overheating

An overheating engine will affect the AC because it is in the engine bay. As the engine temperature keeps rising, so will the whole AC system. It will automatically raise the temperature of the refrigerant, resulting in a less effective AC.

4. Clogged condenser or compressor

The air conditioning system is a closed-loop system that does not allow foreign objects or substances into the system. It does not stop clogs or blockages in the AC, as worn-out internal parts of the compressor can often cause these clogs.

When an internal part of the system breaks, it moves through the system and can cause blockage in the condenser or compressor. 

5. Leakage in AC

You get a low refrigerant when there are leakages in the AC system. As mentioned previously, a low refrigerant will constantly stop the AC functioning.

6. Damaged expansion valve

The expansion valve is an integral part of the AC system, and what it does is it receives the refrigerant in a liquid state and reduces its pressure before being sent to the evaporator.

When the valve is damaged, it either completely closes, not allowing the fluid flow, or it does not allow the correct pressure into the evaporator. It could easily cause the issue of ac not being cold at idleand other ac problems.

How to Fix the Issue of AC

Once you can find out the causes of the AC issue, it is much easier to solve it. All you need to do is fix it according to the cause.

Below are ways to fix an AC that only blows cold when driving.

1. Fix leaks and recharge refrigerant

If you suspect the problem with your AC is low refrigerant, you must first check the refrigerant level. If it is low, then you may need to add more fluids. Then go ahead to the vehicle for any leaks. If you find it, you must have the leak repaired immediately.

2. Faulty expansion valve fix

The best fix for a faulty expansion valve is a replacement; however, you must ensure it is damaged before the replacement. Check the unit power supply; if off, switch it back on. Observe the expansion valve; it must be replaced if it does not start.

3. Damaged compressor fix

To fix a damaged compressor, check its wiring and connections first. Check for corrosion and other forms of wiring problems. If there is any, get it repaired or replaced.

Furthermore, check the clutch compressor for wear or any other severe damage; if it is, it must be replaced. If there is no significant damage, clean the compressor properly and remove all debris.

4. Faulty condenser fan fix

For a faulty condenser, you must ensure it is not a fuse-related issue. Go ahead and crank the vehicle; if the fan rotates, the fuse and relay work. If it does not turn, check the fuse and relay, and replace if damaged. Besides, clean the condenserif dirt accumulates in it.

You can also use a multimeter to test the temperature sensor, fuse, relay, and other electrical components traced to the fan. If you find any damage, replace the affected part.

How Much Does It Cost To Fix Ac Stops Working At Idle

There is no general fixed price to repair an AC that stops working at idle. The cost to fix the problem depends solely on the cause of the problem.

For instance, if the problem with the AC is a leak, it will cost between $150 and $800, depending on where the leak is and how serious it is. If the problem is a compressor problem, it will cost between $200 and $1000, with an additional cost for labor.

Also, if the problem could be traced to a condenser, it would cost between $450 and $1000, including labor for a proper replacement.  


Now that you understand that when your ac gets warm when stopped and not driving is a problem, it is essential to diagnose it correctly before fixing. A professional should handle the diagnosis and fixes to avoid further issues.

Akindayini Temiloluwa

I am Akindayini Temiloluwa, an automotive expert writer and car enthusiast. I have over three years of experience in the automotive writing niche and have completed over 300 pieces of content from 50 projects. I have vast knowledge and skill in vehicle repairing, all mechanical work, car upgrades and maintenance. My goal as an automotive content writer is to simplify the most challenging concepts for my readers, help them self-diagnose what may be wrong with their vehicles and offer real value for their time.

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