Air Conditioner Only Works When Driving – What Could Be Wrong?

Do you ever notice your air conditioner start to malfunction when you are at a stoplight or just sitting still? This can be one of the most inconvenient problems because nobody enjoys sitting in a hot vehicle. Sometimes the A/C works, but only when the car is driving down the road. If this is happening to you, there are several possible reasons and solutions you should consider. We have done the research and compiled a list of potential problems.

Reasons your air conditioning is only working when driving include -

  • A/C Condenser Fan
  • A/C Condenser Blockage
  • A/C Compressor
  • Low Coolant/Freon level

Keep reading below as we break down each of these potential issues and answer other related questions.

A collage of a man in coat driving and mechanic recharging car air-condition in auto repair shop, Air Conditioner Only Works When Driving - What Could Be Wrong?

Possible Air Conditioner Problems

The A/C is responsible for what temperature your car's cabin is and what keeps it there. The A/C is composed of the condenser, compressor, evaporator, dryer, and thermal expansion valve. This means that three items from the list above fall into the category of parts that make up the air conditioner: the A/C condenser fan, possible condenser blockage, and the A/C compressor.

A/C Condenser Fan

The A/C condenser fan's job is to keep the A/C system cool so that it runs efficiently. If it is not working correctly, then there can be many issues. One of the problems may be that your A/C system cannot keep the cabin at the temperature you want. This can include when your vehicle is sitting still because the airflow will be at its worst when the vehicle is not moving.

This will likely cause your air to change temperatures rapidly when your struggling condenser fan is no longer receiving any help from the wind you experience when driving down the highway.

A/C Condenser Blockage

If the fan is not the problem, then there may be an outside source causing the problem. The condenser looks a lot like a vent on the front of a vehicle. If the condenser is clogged or blocked, then the A/C system certainly will not operate properly. Luckily, this may be an easier fix than the other problems because it could just involve cleaning out whatever is causing the blockage.

In this case, you may also notice the A/C system working poorly when the vehicle is stopped because this is when there is the least amount of airflow.

A/C Compressor

Ac compressor coil in a car being removed by a mechanic for cleaning

The A/C compressor is the central part of the air conditioner in a vehicle. There are many problems within it that could cause the whole system to malfunction when the car is stopped. The compressor is where the coils are that cool down the air being pumped into the cabin. If the coils are not cold or require the engine to work harder to cool them down, then they may not be as cold when your vehicle is sitting still.

This is one of the first places a mechanic should check when there are problems with the A/C system.

What Are The Symptoms Of A Bad A/C Condenser?

One of the most common symptoms of a bad A/C condenser is a vehicle overheating when it is idling. The car may be able to keep from overheating when moving because of airflow, but when it is stopped, it is likely to make the problem worse.

This may also cause the A/C air going to the cabin to heat up as the coils inside are unable to stay cold. Warm cabin air can also because the fan is broken and not allowing the coils to be cooled down.

What Are The Symptoms Of A Bad A/C Compressor?

Warm air can be a major symptom of a bad A/C compressor. This is because it is not able to regulate the refrigerant needed to cool down the air. You may notice the car being most affected when stopped, as the engine is not working as hard, and there is no airflow from driving down the highway.

The other symptom of a bad A/C compressor is a loud noise coming from the compressor. There is not a specific noise you should listen for, as there can be any number of sounds coming from a compressor since there are many parts to it.

You will be able to tell if it is coming from the compressor or not by turning the A/C on and off to see if the noise is only being made when the A/C is on.

Low Coolant Level

Mechanic pouring coolant inside engine, What-is-Antifreeze-Used-for-in-Cars

Coolant is meant to help maintain your engine's temperatures. This means if it is cold outside, the refrigerant will help the engine stay at an appropriate warmer temperature. If it is sweltering outdoors, then the coolant will help keep the engine at the desired temperature without overheating.

When coolant levels are low, this function no longer works properly. This will cause your A/C system also to quit working as it relies on coolant to run properly. Depending on your weather conditions, the problem can be exaggerated when your car is idling or stopped.

Why Does My A/C Get Warm At Idle?

Frontside of Toyota Prius hybrid car model 2016 stopping at roadside in autumn

Your A/C is likely getting warm when idling because the refrigerant flow is slower than it is when moving. The same issue can arise with the cooling fan, as it may not be getting the same amount of airflow when the vehicle is stopped.

There may also be a leak in the refrigerant system, and this would cause your cabin air not to work properly. You also want to check for anything that may have gotten into the air condition system as there may be something blocking the air from being cooled off or reaching the cabin.

Where Can I Get My Car's A/C Tested?

Most local auto stores or shops will not only be able to test your car's A/C, but they will do it for free. All you need to do is call stores or mechanics and ask if they will be able to test your A/C system and how much it will cost. This is a common practice because, fortunately, the testing is the cheapest part.

Pep Boys is a popular place to get your A/C tested because they will do it at no cost to you. All you have to do is call and make an appointment, and they will be able to do all the work and more than likely give you a diagnosis if the problem is with the A/C.

If you do not have a Pep Boys in your area, call around to similar shops.

How Much Does It Cost To Fix My Car's A/C?

Car repairing Air Conditioner in car shop, Air Conditioner Only Works When Driving - What Could Be Wrong?

This entirely depends on what is wrong with your A/C system, to begin with. If you need to replace your entire compressor, then you can expect to pay anywhere from $200 to $800 depending on what vehicle you own and where you take it.

If the problem is your condenser fan, you might pay $300 to $500. These are some of the most common repairs, but if you need much more extensive repairs, you may end up paying in the thousands. However, these repairs are uncommon.

Smaller replacements like hoses or sensors may run under $300 if you can find a great deal.


mechanic recharging car air-condition in auto repair shop

All in all, fixing your car's A/C can be a big hassle and can result in having to pay a couple of hundred dollars or a couple thousand depending on the problem. We always recommend taking your vehicle to a professional so they can accurately diagnose your car and fix it well the first time without causing any other issues. If you are experiencing problems with your A/C, it may end up being something small, but it could also be a symptom of a much larger issue. Do not wait to have your vehicle checked out, for the safety of yourself, others, and your wallet!


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