Updated at: 28-02-2023 - By: Sienna Lewis

In your car, you get in, turn on the engine, and then turn on the air conditioning. You’re looking forward to feeling the chilly air on your face. But hold on, it turns out to be simply a little cold air that I thought it would be. It’s then that the air conditioning kicks in. For some reason, it appears like the air conditioning in your automobile only works when you’re driving.

A number of possible explanations exist for why this happened. We’ll show you how your car’s air conditioning system works and why it only works when you’re driving through the details. We will, of course, provide you with a list of possible remedies based on the issue at hand.

  • Its Mechanisms
  • Causes
  • Estimates of costs
  • Conclusion


Let’s take a look at how your car’s air conditioning works. You won’t be able to figure out what’s wrong and why your AC only works when you’re driving if you don’t.

It uses the same components and refrigerants to cool the air as residential air conditioning, which is a lot like how it works. The power source and refrigerant type make a difference. But here’s a breakdown of how it all works:

  1. The drive belt of the engine powers the air conditioning system of the majority of automobiles. In order for the drive belt to move, the engine must be running at the same time. The alternator, the headlights, and the AC’s compressor are all powered by this.
  2. The refrigerant will be compressed by the compressor (in gas form). As a result, it becomes a gas with extremely high temperatures and pressures. The condenser is the next stop.
  3. The condenser then cools the refrigerant by removing the heat and turning it into a liquid. An orifice tube or expansion valve is then used to pump the liquid into.
  4. The refrigerant is re-gasified at the expansion valve. The temperature of the refrigerant will reduce as a result of this action. Onward to a receiver/drier or accumulation device, respectively.
  5. Moisture is removed from the refrigerant by the receiver/drier or accumulator.
  6. The evaporator is the final destination for the refrigerant. External air is drawn into the evaporator core by a blower fan. In this case, only cold air exits the evaporator, and cold air blows out of the vents of your vehicle.

An excellent starting point for learning more about how this system operates is the video provided. It’s the same in every vehicle. Electric cars, on the other hand, do not have internal combustion engines, thus the battery powers the compressor.

AC Only Works When Driving: Causes, Fixes and Costs


With this knowledge, you can better understand how your car’s air conditioner works. The AC in your automobile may only work while you’re driving if one or more of these components fails. The following are some potential contributing factors:


The condenser fan is the most likely culprit. Similar to the radiator fan, the condenser fan is responsible for dispersing heat from the condenser. The temperature of the refrigerant as it flows through the condenser will be reduced if the fans are functioning properly.

Carmakers typically design them to turn on automatically when the engine temperature reaches between 195 and 220 degrees Fahrenheit. It is unlikely that the refrigerant will achieve its optimum evaporator temperature if the fan is not running.

But why does the AC continue to function while the vehicle is in motion? This is because the condenser still receives air from outside the vehicle while you’re driving. In the absence of a fan, this aids in cooling the machine down considerably. When you’re standing still, the condenser can’t be cooled because the fan isn’t working. As a result, the AC is only activated when the car is in motion.


The refrigerant in an air conditioner is expected to stay in the system because it is a closed-loop system. However, the system may have leaks. AC system line cracks or a leak from the condenser could be the cause of this.

Due to their location in the front of the vehicle, condensers are frequently damaged by road debris. A automobile without an under guard is even more vulnerable. When the condenser seals and tubes do wear down, it usually takes between 10 and 15 years for this to occur in most cars.

Leaks in your car’s air conditioning system will eventually cause it to lose refrigerant. The compressor will have difficulty pumping the refrigerant in the system if it falls below the minimal level. However, once the vehicle gains speed, the pump can resume normal operation.


Debris is unlikely to enter the air conditioning system because it is a closed loop. In spite of this, system failures can still occur. This is frequently the result of a malfunctioning compressor’s internal parts.

As a result of the debris being dispersed throughout the system, the compressor or condenser can become clogged. As a result, your air conditioner will run hot since it will have difficulty recirculating the refrigerant.

Refrigerant blockages can also be caused by residue accumulation. The residue will turn into a thick, gooey paste, obstructing air flow and increasing the rate at which heat is radiated. Short cycling can also be caused by a clogged condenser. This occurs when the air conditioning system cycles on and off frequently before it reaches optimum performance.


The parts will wear out more quickly if the system is clogged up. Your car’s air conditioning will malfunction if any of the components in the system are defective.

For example, the compressor clutch may not be cycling due to a broken wire in the clutch coil. If the compressor clutch doesn’t engage, then the compressor itself won’t be able to pump refrigerant throughout the system. In this case, you’ll probably feel the AC not working at all whether you’re idling or driving.

As the evaporator wears out, it may also fail. Leaks may be caused by damage to the evaporator core’s exterior seams. Low refrigerant levels can impede circulation and cause the air conditioning to run warm while idling, as we’ve learned from previous leaks.

Eventually the evaporator will deteriorate, causing leaks. The life expectancy of the three most important components of an air conditioning system is between 10 and 15 years. It’s only natural for these issues to arise in a vehicle of that vintage.


Your engine could be to blame, rather than your air conditioning system, if you’re experiencing this issue. If your engine is overheating, the temperature in the engine compartment, where your air conditioning system is housed, may rise.

Your car’s air conditioning will be affected by the increased temperature since it might boost the temperature of the refrigerant and AC components. All of this implies that your air conditioner must suddenly remove heat that it was never intended to remove.

Air will flow through the engine compartment once the vehicle is moving. Both the engine and the air conditioning system benefit from this. It’s for this reason that, even if your engine is overheating, your air conditioning may still function while you’re driving.

Your engine is overheating if you notice the temperature indicator is higher than usual. The possibility of a malfunctioning water pump or a coolant system leak is just one of many probable explanations. Later, we’ll get into this in further detail.


The air conditioning system in your car has a lot of different pieces to it, so now you know what can be causing a problem in your vehicle. Now that we’ve covered the basics of diagnosing and repairing each problem, let’s move into the specifics:


The problem with the condenser fan is probably the simplest and least expensive to correct out of all the possibilities. There are a number of reasons why the fan may not be spinning on its own:

  • There is a problem with the temperature sensor.
  • When the engine coolant reaches a certain temperature, it is unable to reach that point, and the condenser fan does not turn on.
  • The fan control module is defective.
  • Fuse blown.
  • The fan has stopped working.

The best way to determine if this is an issue is to run your air conditioner and set the blower to MAX. If the fan starts spinning, both the fan and the control module are working properly. Temperature sensors or thermostats may be the source of the problem.

If you have a temperature sensor or thermostat malfunction, you’ll notice engine temperature concerns. It’s possible that the engine will overheat or have difficulty reaching operating temperature. We’ve written in-depth essays on both of these topics, which you can find here:

  • Symptoms of a Faulty Thermostat
  • The temperature sensor for the coolant

Basically, if it doesn’t spin, it’s either a damaged relay, a blown fuse, or the fan motor is faulty. Here’s a step-by-step guide to help you figure out what’s wrong:

How to troubleshoot cooling (radiator) fans is shown in the video to the right of this text. However, the procedure is the same; the only difference is that you must locate the condenser fan rather than the radiator fan

The average cost of repairing a blown fuse or relay is $15. For most automobiles, the condenser fan is between $300 and $425. In the meanwhile, if your issue is with the temperature sensor, a replacement will run you roughly $150. Between $150 to $230 is the average cost of an engine thermostat replacement.


A two-dial pressure gauge is used to check the refrigerant level when you take your car to an auto repair shop for air conditioning work. If the refrigerant level is low, it will be recharged. The typical price ranges from $150 to $300.

Because it’s a closed loop, the air conditioner shouldn’t lose much refrigerant, as previously stated. As a result, if the refrigerant level drops, you may have a leak somewhere in the system.

There is an issue with air conditioning leaks since they can be difficult or expensive to find and repair. A refrigerant recharge may be due soon, so think back to the previous time. A significant leak has most certainly developed in the last year or so, and you should have your mechanic check for it.

However, if the refrigerant lasts over a year, then the leak is relatively small. In this case, we recommend recharging the refrigerant yourself with a refrigerant that has a sealant solution. Take a look at this excellent guide video from ChrisFix:

If, on the other hand, the refrigerant lasts for more than a year, then the leak is little. We recommend replenishing the refrigerant yourself with a sealing solution in this scenario. Take a look at ChrisFix’s amazing how-to video, below:


As previously stated, severe leaks can quickly deplete the AC system of refrigerant. While driving, you may notice that the air conditioning isn’t working properly. You’ll need to fix the AC system in this situation.

Repairing a leak in one of the lines will cost anywhere from $150 to $800. The cost will vary greatly depending on the number of leaks in the system, as well as the brand and model of the vehicle. However, if one of the components is found to be defective, you will have to purchase a new one. Even if you can fix it, it’s not worth it, and you’re better off just buying a new one.

AC Only Works When Driving: Causes & Fix - Manor Racing

The compressor is where we’ll begin. The actual component will cost between $200 and $900. Depending on the difficulty of the project, the additional cost of labor can range from $200 to $500. Expect a new compressor to set you back about $750 on average.

Equally pricey is the evaporator. For starters, you may expect to pay somewhere in the neighborhood of $350. In addition, the cost of labor ranges from $300 to $500. A new evaporator will set you back somewhere between $650 and $1,000.

When it comes to replacing the condenser, it will cost anything from $450 to $950 to do so. These are only general estimates, and the price may be lower or more based on the specific make and model of your vehicle.


You can, and there are a slew of resources available to help you do so. However, whether you’re trying to fix a leak or replace a key component, we don’t suggest doing it yourself. There is a lot of room for error when it comes to these kinds of tasks. In most cases, it’s preferable to leave AC component replacement to the specialists unless you have the proper tools and know-how.


Depending on the cause, you may need to replace the cooling system or repair the engine itself if it is overheating. In addition, you’ll need to act immediately, as overheating can cause extensive engine damage that may require a costly overhaul.

The coolant level is the first thing you should check. If it’s lower than that, you’ve got a leak somewhere in the system. Allow the engine to run for a few minutes after adding fresh coolant. And then check the engine bay for any leaks.

A blown head gasket may be the cause if there is no obvious leak. Having a ruptured head gasket allows coolant to enter the engine’s cylinders, where it will be burned along with fuel, resulting in a rapid loss of coolant. Engine misfires and thick white smoke from the exhaust pipe are two further indicators to watch for.

Even though your coolant level is normal, a malfunctioning cooling system component is most likely to blame for the problem. Radiator caps, radiator fans, water pumps, and thermostats can all fail, resulting in excessive heating. A complete guide to diagnosing an engine overheating is available here.


After you’ve fixed your car’s air conditioning, you’ll want to keep it running smoothly. Fortunately, air conditioning maintenance is rather straightforward. Tips for keeping your car’s air conditioning system in good working order:

  • Install a new cabin filter Between $15 to $50 will be needed for a new set of them. Cabin filters typically need to be replaced every 30,000 miles, so check your owner’s handbook for specifics.
  • Wipe or brush the air vents to remove any accumulated dust and debris. This will keep them out of the AC, where they could cause damage and clogs.
  • If you reside in a location where it’s too cold to turn on the air conditioning while driving, do so once a week for 10 minutes. This helps to keep the gas pressure in the system high enough to keep the compressor running at its peak efficiency.
  • To avoid mildew and other undesirable odors, run the defroster once or twice a week for 5–10 minutes. Excess moisture in the air conditioning system might cause damage if it is not removed.
  • Maintaining it is a must. If you don’t notice any issues with your AC system, it’s good to get it serviced once every two years. There’s nothing wrong with having your AC system serviced once a year for improved peace of mind.


The heater is actually part of the cooling system, not the air conditioning system.. Heating cores are a smaller duplicate of your car’s radiator and are used in your car’s heater. Unless you dismantle your dashboard to get to it, you won’t be able to view this.

A little amount of engine coolant will be diverted into your heater core rather than returning to your radiator when the heater is turned on. A blower fan circulates air through the heater core as the temperature rises. As a result, warm air is blown into your home, where it cools you down.

After a cold start, the heater in your car may not be immediately heated. This is totally normal. Temperature-neutral air will flow past the heater core due to a lack of warm coolant, which prevents the core from heating.

Nevertheless, if the heater does not work even when the engine is running, you most certainly have a leak. A leaking heater core or a leaking heater core entry pipe are the only two possibilities. In either case, the heater is rendered inoperable.

The average cost of a heater core hose replacement, including labor, is between $180 and $210. The heater core, on the other hand, is rather pricey. Including labor, a replacement project can cost anywhere from $560 to $930. Your heater core can be found in our repair instructions here.

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

It’s not uncommon to detect your air conditioner breaking down while you’re at a stoplight or sitting stationary. No one likes to be trapped in a hot car, so this is a major inconvenience. It’s possible that the A/C will only operate while the car is moving. The following are some possible causes and solutions to consider if this is happening to you: There are a slew of potential issues that we’ve identified during our investigation.

If your air conditioner only works when you’re driving, here are some possible causes:

  • AC Refrigerant Recovery Ventilator
  • Blocked Air Conditioning Condenser
  • Compressor for central air conditioning
  • Coolant/Freon levels are too low

We’ll go into more detail about each of these issues and answer any other questions you may have in the following sections.

Possible Air Conditioner Problems

The A/C controls the temperature of your car’s cabin, as well as how long it stays that way. The condenser, compressor, evaporator, dryer, and thermal expansion valve make up the A/C. The A/C condenser fan, a probable condenser obstruction, and the A/C compressor all come under this group of air conditioner components.

A/C Condenser Fan

A/C condenser fans are responsible for ensuring that the cooling system in your air conditioner operates well. Many problems can arise if it isn’t functioning properly. Your A/C system may not be able to keep the cabin at the temperature you desire as one of the issues. When your vehicle is parked, the airflow will be at its worst, therefore this might also apply when you’re driving.

When you’re going down the interstate and the wind stops helping your struggling condenser fan, your air is likely to change temperature quickly.

A/C Condenser Blockage

An outside source may be responsible if there is no fan to blame. There is a condenser on the front of a car that appears like a vent. Having a clogged or obstructed condenser means that the A/C system will not function properly. Fortunately, this problem may be easier to address than the other issues because it may only be a matter of clearing out the obstruction.

You may also notice that the A/C system isn’t operating as well as it should when the vehicle is parked because there is less ventilation at this point.

A/C Compressor

The vehicle’s air conditioner would not function without the A/C compressor. When the vehicle comes to a halt, any number of issues with this system could lead it to fail as a whole. There are cooling coils in the compressor that are used to chill the air that is forced into the cabin. There is a chance that the coils may not be as cold when the car is parked because of a lack of coolant or the engine working harder to cool them.

It’s a good idea for a mechanic to check here first when there are issues with the air conditioning.

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

If your car’s A/C condenser is faulty, it will overheat while you’re sitting in traffic. There is a possibility that the automobile can avoid overheating while moving, but when it’s parked, the problem will certainly get worse.

Coils inside the A/C system may also begin to overheat, causing the air in the cabin to get hotter. It’s possible that the fan is broken, preventing the air conditioning coils from being cooled.

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

A faulty A/C compressor might produce excessively warm air. Inability to regulate refrigerant means it cannot cool the air effectively. When the car is stopped, the engine isn’t working as hard, and there is no airflow from traveling on the highway, so you may feel a decrease in performance.

Loud compressor noise is another sign of a malfunctioning A/C compressor. Compressors can make any number of noises because they have so many moving parts, so you don’t need to pay attention to any one sound.

In order to determine whether or not the noise is coming from the compressor, you will need to turn the A/C on and off.

Low Coolant Level

The purpose of coolant is to keep your engine at a consistent temperature. Using refrigerant will assist keep the engine at a proper temperature if it’s cold outside. The coolant will assist keep the engine from overheating if the weather is hot outside.

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?

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.

This feature ceases to function correctly if the coolant level is low. In order for your A/C system to function properly, it will need coolant. Idling or stopping your automobile can exacerbate the problem, depending on the weather conditions in your area.

Where Can I Get My Car’s A/C Tested?

For the most part, your car’s air conditioner may be tested for free at your local auto store or shop. Asking for an A/C system test and the associated cost can be as simple as calling a local store or mechanic. Because testing is the cheapest phase, this is a frequent practice.

A/C testing at Pep Boys is popular because there is no expense to the customer. A simple phone call to schedule an appointment will allow them to perform all necessary services, including diagnosing the source of your A/C issue.

To find out if your neighborhood has a Pep Boys, make a few phone calls to other comparable businesses.

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

Depending on the problem with your air conditioning system, this may or may not be an option for you. Depending on your car and the mechanic you use, you may expect to pay anywhere from $200 to $800 to repair your compressor.

If your condenser fan is the culprit, you could be looking at a $300 to $500 bill. You may end up paying hundreds of dollars if you need more substantial repairs than this. However, these kinds of restorations are quite rare.

If you can locate a fantastic deal on little parts like hoses or sensors, they could cost less than $300.


There are a number of reasons why your air conditioning only works while you’re driving. The condenser fan and low refrigerant levels are the most straightforward to fix. If you’re experiencing this issue, we suggest starting with those two options.

Changing the fan or the fuse/relay if the condenser fan isn’t operating is necessary if the problem is with the condenser fan. Low refrigerant levels, on the other hand, necessitate a recharge at a cost of $150 to $300.

It’s either a clogged system or a defective component like the compressor, condenser, or evaporator if it is neither. It doesn’t matter what you do, you’ll have to get new ones. There is no point in trying to fix them, and you’d be better off buying new ones.

Even though your air conditioner appears to be working correctly, an overheating engine could be the problem. If the engine is overheating, you must address the issue promptly to avoid an expensive engine rebuild. Whatever the situation may be, we really hope you found this information to be beneficial.


Our crew has put these tools through their paces, and they’re ready to help you fix your automobile at home.

  • Read/Reset OBDII Diagnostics
  • ECU Scanner – Professional
  • Sockets and Connectors
  • Torch
  • Multimeter
  • Charger for a battery
  • Cleaner for the Fuel System
  • The Impact Gun
  • Getting Started Kit
  • Pro Car Jack –
  • Stop the Oil Leak
  • Jumping cables

The AC only works when your car is moving: Top 4 reasons explained and the solutions

In some cases, a combination of factors is responsible for the problem.

1. The condenser fans don’t come on automatically

Cooling systems use condense fans to move heat from refrigerant systems outside. Evaporation occurs after the condenser and before the orifice tube/expansion valve/coil. Condenser fans work to bring the refrigerant’s temperature down to a point where it can condense.

When the engine temperature hits 195°F to 220°F, they are meant to start rotating. With the use of an engine temperature sensor, this feature is made feasible.

When the condenser fan fails, the next step is to inspect the relays and fuses. As a last step, check for corroded or loose connections, shorts, and open circuits in the cars’ wiring. It is clear that the fan has died if the fan socket is receiving enough power.

Temperature switch failure, coolant sensor malfunction, or a clogged thermostat could all be to blame for the death of a car’s air conditioning system fan. A broken fan control module and a malfunctioning fan motor could be to blame for all of your woes, according to the experts here.

Cranking the engine and turning the AC up to MAX is the fastest and easiest approach to diagnose problems with the fan circuit. This means the fan motor and wiring, as well as the fuses and relays, are working properly. There is insufficient information to rule out temperature sensor and PCM concerns from the test results.

Using a multimeter, check the resistance of the temperature sensor if you have any questions. Checking for defective relays and blown fuses may also be done using the multimeter. It can also be used to check the continuity of the fan wiring.

With fan motor troubleshooting, jumper cables are your only hope. Unplugging the fan’s wire connections and using jumper cables from the battery to transfer power to the fan can rule out this problem. Even at normal speed, a working fan motor will perform properly. Despite being provided with 12V of power, a malfunctioning fan motor will run at a slower rate than planned.

Affected components, including sensors, thermostats and other relays and fuses, must be replaced in order to get the vehicle’s AC back to working order. Replacement or repair of the fan motor is an option, as is having it rebuilt by a trustworthy expert. Bolts and nuts can be tightened to prevent loose connections from causing wiring problems. Adding baking soda to a water solution can also help eliminate rust from corroded wires.

2. Low refrigerant charge

When the system’s refrigerant levels drop too low, the compressor is shut off via a low-pressure switch. Furthermore, in order to avoid a catastrophic failure, AC compressors require a continuous oil supply.

Refrigerant charge faults can be fixed by following these suggestions.

  • Turn on the air conditioning, crank up the engine, and lower all the windows.
  • Allow a minimum of ten minutes for the engine to reach its optimal operating temperatures while it is idling with the blower speed set to 2.
  • Observe the temperature and moisture content of the AC pipe located within engine compartment. Condensed water should be visible and feel chilly to the touch on the pipe.
  • Take a look at the pipe near the firewall. It’s possible that the gas volume is low if the temperature is lower than normal.

Your refrigerant’s gas volume is determined by a two-dial pressure gauge. To get the readings, the instrument is linked to both the high- and low-pressure lines. If you’ve got the time and inclination, you can do it on your own. The best course of action is to have the depleted refrigerant refilled.

As long as there is no other problem, charging it through the low-pressure port with the compressor still engaged is the best approach. In this case, DIY recharge kits are employed. But if the refrigerant level is low, the clutch will not be able to engage at all.

Using the low-pressure switch to compel the compressor clutch to engage while recharging is not recommended since the compressor may be running with little or no oil. However, you’ll have to pay for the compressor if it accepts the payment.

Know how to recharge the freon in your air conditioner. Otherwise, it’s best to seek out the assistance of a specialist.

3. The compressor clutch is not cycling

It is the job of the compressor clutch to hold the compressor shaft in place. The air conditioning compressor will not be able to pump refrigerant if this component breaks.

Turn on the AC and crank the engine to see if the compressor clutch is working. At this point, the clutch and the pulley should be spinning in tandem. When the system’s only moving part is the pulley, there is a serious problem. There are a number of reasons why the clutch may not engage.

The problem could be the result of an open circuit due to a damaged clutch coil wire, blown fuses, a defective clutch coil, or a faulty ground. Also, a low-pressure lockout may be to blame. A multimeter can help you identify the specific components that aren’t working.

Replace the faulty part to get your car back to normal operation. By tightening the nuts and bolts, you can avoid problems with loose connections. Grounding concerns can be resolved by modifying the wiring, thereby rectifying the error caused by the live wire’s contact with the earth wire..

Do I need to add oil to my car’s AC compressor when recharging it?

5 Main Causes Of AC Only Works When Driving - DrivingPress

4. The compressor might be blocked or dirty

Keeping the refrigerant flowing between the evaporator and condenser coils is the job of the compressor.

A visual inspection of the AC line, condenser, and compressor will reveal any leaks. You’ll see a buildup of dust caused by oil sedimentation in the vicinity of the leaky pipes. Check the AC filter to see whether dust has accumulated and obstructed it.

A pressure washer can be used to wash out the condenser through the bumper’s apertures. If dirty water is dripping from the compressor, it is likely clogged. The condenser is vulnerable to damage if the washer jet is pointed directly at it. Spread it out instead. It may be in your best interest to have the radiator washed by a professional at a car wash. After this, your car’s air conditioning will function normally again.

Get the OBD2 codes for your AC system if you’d like. Here, you may look up AC system OBD2 codes.


Cranking the engine and turning the AC up to MAX can reveal any problems with the fan, compressor clutch, or low refrigerant charge. Make a note of whether or not the clutch is rotating in conjunction with the pulley when the fan is functioning.

Wiring-related issues are the most common cause of air conditioning system malfunctions. It is simple to spot problems such as blown fuses, bad temperature and coolant sensors, broken thermostats, bad relays, short and open circuit with a multimeter.

Visual testing can also be used to identify corroded cables. Replace the faulty parts or use a baking soda and water solution to clean the wires.