AC Only Works When Driving

AC Only Works When Driving: What’s Causing It?

You get in your car, turn the engine on, and then switch on the AC. Expecting a nice cool breeze sweeping your face. But hang on, the air turns out to be only very mildly cold. Then you drive along and now the air conditioning is working. Seems that your car’s AC only works when driving, why is this?

There are several possibilities on why this might have happened. We’ll talk you through the components inside your car’s air conditioning system, how it works, and why your AC only works when driving. And of course, we’ll list down the solutions depending on the problem you have.

In this guide, you’ll find a detailed explainer of why (as well as the primary causes and reasons) your car’s AC only works when driving, and not when idling or stationary. Moreover, we’ll discuss how you can diagnose and troubleshoot this issue yourself, as well as what sort of repairs (and their costs) you might need to consider.

We’ll even go into detail with other, similar or relevant car AC problems, and how to fix those, in addition to when your car’s AC only works when driving. This too will allow us to dive deep into the diagnosis and troubleshooting steps for each one of those to get your car’s air conditioning unit working right again.

AC Only Works When Driving: How The Car AC Works

Let us explain how the air conditioning system in your car works. Otherwise, you won’t be able to make heads or tails of what might be wrong and why your AC only works when driving.

It works largely similarly to how home air conditioning works; they use the same components and refrigerants as a means to cool the air. The difference is in the power source and the type of refrigerant used. Anyway, here’s how the system works:

  1. Most car air conditioning system is powered by the engine via the drive belt. When your engine is running, it will also run the drive belt. This powers a number of electrical accessories, including the alternator, the headlights, and the AC compressor.
  2. The compressor will compress the refrigerant (in gas form). This transforms it into a high-temperature and high-pressure gas. It will then enter the condenser.
  3. The condenser then removes heat from the refrigerant and transforms it into a liquid. Afterward, it pushes the liquid into an expansion valve or sometimes called an orifice tube.
  4. At the expansion valve, the refrigerant returns to its original gas state. As the refrigerant does this, it will drop down in temperature. Afterward, it travels into a receiver/drier or accumulator.
  5. The receiver/drier or accumulator dries the refrigerant by removing moisture.
  6. Finally, the refrigerant gets to the evaporator. A blower fan will pull air from the outside and blow it through the evaporator core. This results in only cold air flowing beyond the evaporator, and cold air blowing through your car’s vents.

We recommend watching the video above to get a better understanding of how the system works. And it’s pretty much the same in every car. Although in electric cars, the compressor is powered by the battery, since there’s no internal combustion engine.

AC Only Works When Driving: Possible Causes

So, now you know how your car’s air conditioning system works. Some of these components may fail which could be the reason why your car’s AC only works when driving. Here are the possible causes (and in addition to the primary causes, we’ll also dive into the specific symptoms, diagnosis, troubleshooting, and repair/replacement steps for each component):

1. Faulty Condenser Fan

The most likely culprit is the condenser fan. The condenser fan is responsible for dissipating heat from the condenser, similar to how the radiator fans work. If the fans work properly, it will reduce the refrigerant’s temperature as it passes the condenser.

Carmakers usually design them to turn on automatically once the engine reaches operating temperature, which is somewhere around 195°F to 220°F. If the fan doesn’t come on, then the refrigerant won’t drop to an ideal temperature by the time it reaches the evaporator.

But why does the AC still works when driving? This is because when you’re driving, air from outside of the car will still pass through the condenser. This helps to cool it down, even without the fan. But since the fan isn’t working, there’s no air to cool down the condenser when you’re stationary. Hence why the AC only blows cool air when the vehicle is moving.

1.1. Symptoms of a Faulty Condenser Fan

You may notice your AC only provides cold air while the car is in motion. At a standstill or while idling, the AC may start blowing warm air. In addition, if your condenser fan is not operating, you might notice your engine temperature increasing due to less effective heat dissipation.

1.2. Diagnosing and Troubleshooting the Problem

You can check the condenser fan operation by turning on your AC and then observing the fan. If the fan doesn’t turn on after a while, there might be a problem. An electrical issue, such as a blown fuse or a bad relay, could be causing the fan not to start. If these are in good condition, the fan motor might be the problem.

1.3. DIY Fixing/Repair Tips

If the fan motor is bad, you’ll likely need to replace it. First, disconnect the battery. Then, locate the condenser fan (usually near the radiator) and disconnect the electrical connector. Remove the fan by unscrewing the bolts holding it in place and then install the new one.

Connect the electrical connector and reconnect the battery. If you’re uncomfortable doing this, a mechanic can perform the replacement.

2. Low Refrigerant Level

The AC system is a closed-loop system, meaning it’s not supposed to lose the fluid – in this case the refrigerant – in it. However, leakages may occur in the system. This could be because of cracks in the AC system line, or a leak from the condenser.

Condensers are prone to damage from road debris since they usually sit at the front of the car. This is especially true if the car doesn’t have any under guard. Even if it does, the seals and tubes of the condenser can wear down, but in most cars, it will take somewhere between 10 – 15 years for this to happen.

In any case, leaks mean your car’s air conditioning system will lose refrigerant over time. Once it’s below the minimum level, the compressor will struggle to pump the refrigerant into the system, especially when idling. But as the car builds up speed, it can pump again as normal.

2.1. Symptoms of Low Refrigerant Level

You may notice your AC not cooling effectively, especially while idling. The air blowing out may feel lukewarm or even hot. A refrigerant leak can sometimes cause a hissing noise coming from the AC components.

2.2. Diagnosing and Troubleshooting the Problem

Check the AC pressure using an AC pressure gauge. Low pressure could indicate a refrigerant leak. You can visually inspect the AC components for signs of leaks, such as oily residue.

2.3. DIY Fixing/Repair Tips

If you have a leak, you can use a refrigerant leak sealer, but this is usually a temporary fix. To properly repair the leak, you may need to replace the damaged part. Recharging your AC with refrigerant can be done with a recharging kit, but be careful not to overfill. If you’re uncertain, consult a mechanic.

3. Clogged Condenser Or Compressor

Since the air conditioning system is a closed-loop system, it’s unlikely for debris to get into it. However, blockages can still happen inside the system. This is often due to a worn compressor where the internal parts are breaking down.

When internal parts in the compressor break away, it will disperse this debris throughout the system, causing blockages in the condenser or compressor itself. And this means that the system will struggle to recirculate the refrigerant, causing your AC to be warm.

Also, the build-up of residue in the refrigerant may also cause blockages. The residue will turn into a sticky paste, causing circulation issues, as well as disturbing the heat dissipation process. Additionally, a blocked condenser can also cause short cycling. This is when the air conditioning system cycle on and off rapidly before it could reach optimal operation.

3.1. Symptoms of a Clogged Condenser or Compressor

Your AC might not cool effectively, and you may notice the AC system cycling on and off rapidly. You might also notice an increase in engine temperature due to reduced heat dissipation.

3.2. Diagnosing and Troubleshooting the Problem

A professional can use an AC gauge to check the system’s pressures, which can indicate a blockage. Inspecting the AC components visually for debris can also help diagnose a clog.

3.3. DIY Fixing/Repair Tips

A clogged condenser or compressor often requires professional service or replacement. Cleaning the system and replacing the refrigerant may help, but if the compressor is worn out, it may need to be replaced.

4. Other Faulty Parts

If you have blockages in the system, it will likely wear out the parts much quicker as well. When the parts in the air conditioning system are faulty, it will cause problems with your car’s air conditioning.

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 mentioned, the condenser can wear down over time as well. There may be leaks from the seals or the tubes. Or it may also experience coil damage, which is the part responsible for removing heat.

The evaporator may also break over time. There may be damage to the outer seams of the evaporator core, which will cause a leak. And as we’ve learned, leaks will lead to low refrigerant levels which disrupt the circulation and can cause the air conditioning to be warm when idling.

The evaporator may also corrode over time, which will cause leaks as well. These three major components of the air conditioning system typically last for about 10 – 15 years. If your car is around that age, it’s to be expected to start experiencing these problems.

4.1. Symptoms of Faulty AC Parts

The symptoms depend on the specific part. For example, a faulty compressor clutch might cause the AC not to cool at all. Faulty parts can lead to the AC system not cooling effectively or the system cycling on and off rapidly.

4.2. Diagnosing and Troubleshooting the Problem

Inspecting the AC components visually and listening for unusual sounds can help identify issues. A professional can also use diagnostic tools to pinpoint the problem.

4.3. DIY Fixing/Repair Tips

Replacement is often the best solution for faulty parts. The process depends on the specific part, but usually involves removing the old part and installing a new one. Be sure to disconnect the battery before doing any repairs.

5. Overheating Engine

It’s also possible that the problem isn’t coming from the air conditioning system itself but from your engine. If your engine is overheating, this will raise the temperature within the engine bay, which is also where your air conditioning system is located.

The higher temperature will affect your car’s air conditioning since it can raise the temperature of the refrigerant and components of the AC system. All this basically means your AC system now has to remove excess heat that it wasn’t designed to in the first place.

AC Only Works When Driving

When the car starts moving, air will go through the engine bay. Helping to cool down both the engine and the AC components. This is why even if you have an overheating engine, the air conditioning may still work when you’re driving – thanks to the outside air going through the engine.

If you notice your temperature gauge sitting higher than usual, then you have an overheating engine. There are several possible causes, such as low coolant, coolant system leak, and a faulty water pump amongst other causes. We’ll get into this further later on.

5.1. Symptoms of an Overheating Engine

An overheating engine can cause the temperature gauge to read high. You may notice steam from the engine bay. The AC might also perform poorly, especially while idling.

5.2. Diagnosing and Troubleshooting the Problem

Check the coolant level in the radiator (but be careful – never open a hot radiator). A low level can indicate a coolant leak. You can also inspect the water pump and radiator for leaks.

5.3. DIY Fixing/Repair Tips

Add coolant if the level is low. If you have a leak, you might be able to seal it temporarily with a radiator stop leak, but you should have the leak repaired professionally. A faulty water pump typically needs to be replaced, which usually involves removing the old pump and installing a new one. Again, consult a mechanic if you’re unsure.

AC Only Works When Driving: Repair Cost Estimates

So, now you know the parts inside the air conditioning system, and what might be causing a problem in your car. Now, let’s get into how to diagnose, and the repair cost estimates for each problem:

Condenser Fan Repair Cost

The condenser fan problem is probably the easiest and cheapest one to fix all the possible problems. When the fan doesn’t spin automatically, there are several possible causes:

To diagnose this problem, turn on your AC and turn the blower to the MAX position. This will trigger the fan to spin, and if it does, then your fan and its control module are fine. This means the problem lies either with your temperature sensor or thermostat.

Keep in mind that when you have a temperature sensor or thermostat problem, you’re likely to notice engine temperature issues. The engine may either overheat, or it will struggle to get to operating temperature. We’ve written comprehensive articles about the two components and you can read them here:

If it doesn’t spin, then it’s either a blown fuse, a bad relay, or the fan motor is broken. Here’s how you can diagnose the problem further:

The video above shows how to diagnose the cooling (radiator) fans. But the method is the same, you just need to locate the condenser fan rather than the radiator fan.

Replacing a blown fuse or relay usually costs no more than $15. As for the condenser fan, it costs between $300 – $425 for most cars. Meanwhile, if your problem lies with the temperature sensor, it’ll cost about $150 to replace it. And an engine thermostat replacement usually costs between $150 – $230.

Low Refrigerant And Leaks Repair Cost

When you go to an auto repair shop for an air conditioning service, the first thing they will do is check the refrigerant level using a two-dial pressure gauge. If the level is low, they will recharge the refrigerant. This service usually costs between $150 – $300.

But as mentioned, the air conditioning system is a closed-loop system and it isn’t supposed to lose refrigerant – at least not by much. So when the refrigerant is low, it’s likely you have a leak in the system.

The problem is that air conditioning leaks can be difficult to identify, and repairing them is likely to be expensive. Try recalling when was the last time you had a refrigerant recharge. If it’s been less than a year, then it’s likely there’s a big leak and you should ask your mechanic to find the leak.

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:

The refrigerant costs about $32 for a 20oz can. It’s relatively easy to use and we recommend doing it yourself, so you don’t have to pay for the $150 – $300 service at an auto repair shop.

Replacement Cost For Air Conditioning Parts

As mentioned, major leaks can cause the AC system to lose refrigerant quickly. Broken components in the AC system can also cause the AC to only work when you’re driving. In this case, you’ll have to repair the AC system.

If there’s a leak in one of the lines, it will cost anywhere between $150 – $800 to repair the leak. The cost will depend heavily on how many leaks are present in the system, as well as your car’s make and model.

However, if it turns out that one of the components is broken, you’re going to have to replace it. You might be able to repair it, but it’s not going to be worth it and you’re better off replacing the component altogether.

We start with the compressor. The part itself is going to cost somewhere between $200 – $900. While labor will cost another $200 – $500, depending on how difficult the job is. On average, expect a compressor replacement to cost you somewhere around $750.

The evaporator is equally expensive. Prices start at around $350 and can go as high as $500. While labor also costs somewhere around $300 – $500. In total, you’ll have to pay somewhere between $650 – $1,000 for an evaporator replacement.

Meanwhile, the condenser will cost around $450 – $950 to replace, including labor. These are just rough estimates and it may be cheaper or more expensive, depending on your car’s make and model.

Can I Fix Or Repair It Myself?

You can, there are tons of guides out there on how to replace the AC components in your car. However, we don’t recommend doing it yourself, whether to fix a leak or to replace major components. They’re quite difficult to do, and it’s easy to get it wrong. Unless you have the right tools and good mechanical skills, replacing AC components is probably the best left for professionals to do.

AC Only Works When Driving: If Your Engine Is Overheating

If it turns out the problem is an overheating engine, then you’ll need to address either the cooling system or the engine’s internals. And you’ll need to do this quickly, as overheating can cause excessive damage to the engine which could lead to an expensive engine rebuild.

AC Only Works When Driving

The first thing you need to check is your coolant level. If it’s below the minimum level, then you have a leak in the system. Refill your coolant, and then let the engine run for a few minutes. And then see if there are any leaks in the engine bay.

If there’s no visible leak, then it’s possible you have a blown head gasket. If you have a blown head gasket, it will allow coolant to enter the engine’s cylinders and it will be burnt along with fuel, causing you to lose coolant rapidly. You will notice other symptoms as well, including engine misfires and thick white smoke coming out of the exhaust pipe.

However, if your coolant level is normal, then you probably have a faulty component in the cooling system. Your overheating problem may be caused by a bad radiator cap, broken radiator fan, faulty water pump, or a broken thermostat. We wrote a comprehensive guide on how to diagnose an overheating engine and you can read about it here.

How Do I Maintain My AC?

Once you’ve fixed the air conditioning in your car, you’re going to want to maintain it. Thankfully, air conditioning maintenance is relatively easy. Here are our tips on maintaining your car’s AC system:

  • Replace the cabin filter. It will cost between $15 – $50 to replace them. Check your owner’s manual on when to change your cabin filter, but usually, you’ll have to replace them every 30,000 miles.
  • Clean dust and debris from the air vents by wiping them or using a brush. This will prevent them from getting into the AC system which can clog and damage the system.
  • If you live in a cold area where it’s too cold to turn on the air conditioning when you drive, turn it on for 10 minutes once a week. This helps to maintain gas pressure inside the system and keep the compressor working properly.
  • Run the defroster once a week for 5 – 10 minutes to prevent mildew and other unpleasant odors (for more insight, check out our guide on how to get mildew smell out of car). This will also help to clear away excess moisture in the air conditioning system, which can damage it over time.
  • Service it regularly. Servicing your AC system once every two years is fine, especially if you don’t see any problems. But for better peace of mind, there’s nothing wrong with servicing your AC system once a year.

What If I Have A Heater Problem?

The heater is actually a part of the cooling system and not the AC system. Your car’s heater works by using a heater core, which looks like a miniature version of your car’s radiator. This sits behind your car’s firewall, so you won’t be able to see it unless you take apart your dashboard.

When you turn the heater on, your car’s cooling system will divert some of the hot coolants from your engine into the heater core, rather than back to the radiator. This raises the heater core’s temperature, and a blower fan will blow air through it. The resulting air becomes warm, which is then directed to your air conditioning vents.

AC Only Works When Driving

If your car’s heater isn’t immediately warm when you turn on the engine from a cold start, this is perfectly normal. This is because the coolant is still cold, which means it won’t heat up the heater core, resulting in ambient temperature air being blown through it.

But if the heater still doesn’t work even though the engine is at operating temperature, you likely have a leak somewhere. Either the heater core itself is leaking, or the entry pipe of the heater core is leaking. Either way, this results in the heater not working.

A heater core hose replacement usually costs around $180 – $210 including labor. Meanwhile, the heater core itself is quite expensive. A replacement job costs somewhere around $560 – $930 including labor. You can learn more about your car’s heater core in our repair guide here.

AC Not Working In Car

Besides the primary issue that we’re discussing here, where your AC only works when driving, there are other, similar air-conditioning problems that you might encounter. For instance, you might have an issue where your AC works fine when driving but only blows out hot air – no cold air.

Or, you might encounter issues where the AC unit doesn’t work at all. Alternatively, there are more minor woes, that are equally annoying, such as when a car’s AC works fine but takes a really long time to get properly cold. This section will discuss some of these common (related) issues, as well as their symptoms, causes, diagnosis, troubleshooting steps, and how you can fix them:

1. AC Only Blows Cold When Driving


The AC in your car works fine when the vehicle is in motion, but when you are idling or the car is stationary, the air begins to warm up. This could be a subtle shift, with the air growing gradually warmer, or a noticeable change, with the AC suddenly blowing hot air.


This issue is often due to a malfunctioning fan or insufficient refrigerant in the AC system. The condenser fan helps cool the refrigerant when the car is not moving. If the fan is not working properly, the refrigerant won’t cool enough to provide cold air. Low refrigerant could also cause the AC to blow warm air, especially when the car is idle.

Diagnosis & Troubleshooting:

You can check if the condenser fan turns on when you switch on the AC while the car is stationary. If it doesn’t, that could be the issue. You can also check the refrigerant level. A professional mechanic will have the tools to do this safely.

Repair & Maintenance:

If it’s the fan, you’ll need to replace it. If it’s the refrigerant, a recharge may be necessary. It’s crucial to regularly service your car’s AC system, which includes checking the refrigerant level and the functioning of various components.

2. AC Only Works When Driving Fast


Your AC only seems to work properly when driving at high speeds. The air feels warm or not as cool when you’re driving slowly or idling.


The primary cause could be a faulty condenser or cooling fan. At high speeds, the natural airflow is enough to cool the condenser, but at lower speeds, the fan is needed. If it’s malfunctioning, you will notice the difference.

Diagnosis & Troubleshooting:

Check if the cooling fan is operational when the car is idling with the AC on. If it’s not, you may have found your culprit.

Repair & Maintenance:

Replace a faulty fan and ensure regular AC system maintenance. This includes checking the fan, condenser, and refrigerant levels.

3. AC Only Works When Driving Slow


The AC works when the car is moving at a slow pace or is idle, but it blows warm air when the vehicle is at high speeds.


This could be due to a leak in the AC system that reduces the pressure when the vehicle moves quickly. It could also be a result of a blocked or dirty condenser that can’t handle the increased heat at high speeds.

Diagnosis & Troubleshooting:

Check for leaks in the AC system and examine the condenser for blockages or dirt.

Repair & Maintenance:

Repair any leaks, clean, or replace a dirty condenser, and maintain regular service for your AC system.

4. AC Only Works When Accelerating


You may notice that your car’s AC only seems to function correctly when you’re accelerating or under high engine load.


The cause can be a vacuum leak. Under acceleration, the engine produces more vacuum, which might be enough to compensate for the leak and make the AC function normally. Another possible cause is a weak AC compressor clutch that is unable to engage fully at idle but does so under acceleration.

Diagnosis & Troubleshooting:

You can check for vacuum leaks with a vacuum gauge or by using a smoke machine. Alternatively, inspect the AC compressor clutch for wear or damage.

Repair & Maintenance:

Repair any detected vacuum leaks or replace a worn AC compressor clutch. Regular maintenance and inspection of the AC system can help prevent these issues from arising.

5. AC Only Works on High


Your car’s AC only seems to work on the highest setting, with nothing coming out on lower settings.


This could be due to a problem with the blower motor resistor, which controls the speed of the blower fan. If it’s malfunctioning, it might only work at the highest setting.

Diagnosis & Troubleshooting:

A multimeter can be used to test the resistor. If it’s faulty, it will need replacement.

Repair & Maintenance:

Replace a faulty blower motor resistor. Regular maintenance checks can identify this issue early on.

6. Car AC Not Blowing Cold Air


Your car’s AC is blowing air, but it’s not cold.


This could be due to low refrigerant levels, a malfunctioning compressor, a clogged condenser, or a leak in the system.

Diagnosis & Troubleshooting:

Check the refrigerant level and inspect the compressor and condenser. A professional mechanic can detect leaks using specialized equipment.

Repair & Maintenance:

A recharge might be necessary if the refrigerant level is low. A malfunctioning compressor or clogged condenser will need repair or replacement. Regular service checks will help ensure your AC works optimally.

7. Car AC Blowing Warm Air


The AC in your car is blowing warm or hot air instead of cold air.


This could be due to a refrigerant leak, a faulty compressor, a broken condenser, or a malfunctioning AC temperature control switch.

Diagnosis & Troubleshooting:

Check for leaks, test the compressor, and inspect the condenser. The AC temperature control switch can also be tested for proper operation.

Repair & Maintenance:

Repair any leaks or replace the faulty parts as necessary. Regular maintenance checks of your AC system can prevent these issues from occurring.

8. Car AC Takes a While to Get Cold


The AC eventually blows cold air, but it takes a noticeably long time after being switched on.


A slow-cooling AC may be due to low refrigerant levels, a dirty or clogged condenser, or a worn compressor.

Diagnosis & Troubleshooting:

First, inspect the condenser for any dirt or blockages. Check the refrigerant levels, and examine the compressor for any signs of wear or damage.

Repair & Maintenance:

Refill the refrigerant if it’s low. Clean the condenser, or replace it if it’s too damaged. If the compressor is worn out, it may need replacement. Regular maintenance of your car’s AC system can help prevent these issues.

9. Car AC Suddenly Stopped Working


Your car’s AC was working fine and then suddenly stopped blowing cold air.


This could be due to a sudden refrigerant leak, a broken condenser, or a failed compressor.

Diagnosis & Troubleshooting:

A mechanic can use leak detection tools to check for refrigerant leaks. Check the compressor for any signs of failure, and inspect the condenser for any damage.

Repair & Maintenance:

Repair any leaks, and replace any broken or failed parts as necessary. Regular check-ups and timely repairs can prevent sudden failures.

10. Car AC and Heat Not Working


Neither the AC nor the heating systems in your car are functioning.


This could be due to a problem with the blower motor, a malfunctioning thermostat, or issues with the HVAC control head.

Diagnosis & Troubleshooting:

Check the blower motor and thermostat for operation. If both are fine, the issue might lie with the HVAC control head.

Repair & Maintenance:

Replace the malfunctioning part as necessary. Regular inspection of the car’s HVAC system can help identify and prevent these issues.

11. Car AC Sometimes Works Sometimes It Doesn’t


Your car’s AC works inconsistently, blowing cold air at times and warm air at other times.


This could be due to intermittent electrical issues, a failing compressor, fluctuating refrigerant levels due to a slow leak, or a malfunctioning AC control switch.

Diagnosis & Troubleshooting:

You can check the electrical connections, inspect the compressor, check the refrigerant levels, and test the AC control switch.

Repair & Maintenance:

Tighten any loose connections, replace a failing compressor, refill the refrigerant, or replace a malfunctioning AC control switch. Regular maintenance can help identify these issues early and keep your car’s AC running smoothly.

AC Only Works When Driving Essential Knowledge

  1. The AC compressor is responsible for circulating refrigerant throughout the AC system.
  2. A blockage in the AC system can prevent air from flowing and cause the AC to only work when the car is moving.
  3. A Freon leak can cause the AC to only work when the car is moving.
  4. A faulty compressor clutch can prevent the compressor from engaging and cause the AC to only work when driving.
  5. AC units are only designed to work in wet weather, not dry weather.
  6. A faulty blower motor or clogged expansion valve can cause the AC to only work when driving.
  7. Low refrigerant charge, a damaged compressor or AC line, and faulty seals can also cause a Freon leak.
  8. The compressor and condenser may not be getting enough airflow while the car is stopped, causing the AC to work better while driving.
  9. The AC fan may not be working properly if it only works while driving, and it could be due to dirty blades, a defective motor, low fan speed, or a blockage.
  10. The recirculate setting on an AC system is designed to save energy by reusing air already inside the car but can cause the AC to stop working when the car is not moving.

AC Only Works When Driving: In Conclusion

There are several possible causes of your AC only working when driving. The easiest ones to diagnose are the condenser fan and low refrigerant levels. We recommend taking a look at those two first if you have this problem.

If it’s the condenser fan isn’t working, then you’ll need to replace the fan – or the fuse/relay if it turns out that’s the cause. Meanwhile, low refrigerant levels mean you’ll have to recharge it, which costs around $150 – $300 at an auto repair shop.

If it is neither of the two, then you either have a clogged system, or a faulty component such as the compressor, condenser, and evaporator. In any case, you’re going to have to replace them. Repairing them is not going to be worth it, and you’re better off replacing them.

And finally, if your air conditioning system seems fine, then an overheating engine might be the cause. In this case, you’re going to have to troubleshoot the overheating problem and solve it immediately before it turns into an expensive engine rebuild. In any case, we hope this article has been helpful to you.

AC Only Works When Driving: Frequently Asked Questions (FAQs)

Here are some popular questions and answers around the issue of when a car’s AC only works when driving…

Does AC Use Gas

Yes, using the AC in your car does consume gasoline. The air conditioning compressor runs off the engine’s accessory belt, which requires energy, and that energy is derived from the combustion of gasoline within the engine. This energy demand will increase fuel consumption. However, the specific impact on gas mileage can vary greatly depending on a number of factors, such as the age and type of your vehicle, the efficiency of your AC system, and the outdoor temperature.

How Much to Fix AC in Car

The cost of fixing a car’s AC can range widely, typically from $200 to $800, depending on the specific problem. If the issue lies with a minor part like a fuse or relay, the repair could be on the lower end of that range. However, if more extensive repairs or parts replacements are needed, such as a new compressor, costs can rise significantly.

How to Fix AC in Car

Fixing a car’s AC can involve several steps depending on the issue at hand. It might include recharging the refrigerant, replacing the AC compressor, fixing leaks, or cleaning and repairing the condenser. It’s always recommended to diagnose the problem correctly first, possibly with the aid of a mechanic or a professional AC technician. Remember that working with AC systems can be complex and sometimes dangerous due to the high pressure and refrigerants involved.

Why Is My AC Not Working

There could be various reasons why your car’s AC is not working. It could be due to a low refrigerant level, a faulty compressor, a blocked condenser, an electrical issue, or a leak in the system. In some cases, the problem could also be due to a failing blower motor or issues with the AC controls inside the vehicle.

How to Fix Car AC Not Blowing Cold Air

If your car’s AC is not blowing cold air, the first step is to check if it’s low on refrigerant and recharge it if necessary. If that doesn’t help, inspect for leaks in the system. Other potential issues might be a clogged condenser, a faulty compressor, or an electrical problem. These components may need to be cleaned, repaired, or replaced. It’s advised to seek the help of a professional if you’re unsure.

How to Make AC Colder in Car

To make the AC colder in your car, ensure it’s properly maintained. Regular servicing can help, including checking the refrigerant levels and recharging if necessary, cleaning or replacing the cabin air filter, and inspecting the condenser for any blockages. Avoid setting your AC to the maximum setting immediately, as it can strain the system. Instead, start at a lower setting and gradually increase it.

How Does Car AC Work

A car’s AC works on the principle of evaporation and condensation. It consists of several parts including the compressor, condenser, expansion valve, and evaporator. The compressor pressurizes the refrigerant, turning it into a hot, high-pressure gas. This gas is cooled in the condenser and converted into a high-pressure liquid. The liquid then passes through the expansion valve, reducing its pressure and temperature before entering the evaporator, where it absorbs heat from the car’s interior and evaporates back into a gas. The cycle then repeats.

Why Is My AC Blowing Warm Air in My Car

If your AC is blowing warm air, it could be due to low refrigerant levels, a failing compressor, a clogged condenser, or electrical problems. In some cases, it may also be due to a problem with the blend air door inside the dashboard. A professional inspection can help identify the exact cause and determine the necessary repairs.

Does Coolant Affect AC

While coolant and refrigerant are two different fluids that serve different systems in your car (coolant for the engine cooling system and refrigerant for the AC system), a malfunctioning cooling system can indirectly affect the AC. If the engine is overheating due to a coolant issue, it may cause the AC to perform poorly or shut down to prevent further strain on the engine.

Why Does My Car AC Only Get Cold When I Accelerating

If your car’s AC only gets cold when accelerating, it could be due to low refrigerant levels, a failing compressor, a clogged expansion valve, or problems with the electrical controls. When you accelerate, the engine provides more power to the AC system, which can temporarily overcome these issues. However, a thorough diagnostic should be performed to find the root cause of the issue.

How Much Gas Does AC Use While Parked

Running your car’s AC while parked will consume gas, but the exact amount can vary based on factors like the efficiency of your AC system, the outdoor temperature, and the idling efficiency of your vehicle. In general, running the AC while idling consumes less fuel than when driving, but it’s still not a fuel-efficient practice.

What Does a Car Condenser Do

The condenser in your car’s AC system plays a crucial role in dissipating heat. It transforms the high-pressure hot refrigerant gas coming from the compressor into a cooler high-pressure liquid. This process is critical to the operation of your AC system. If the condenser is damaged or blocked, it can prevent the AC from cooling effectively.

Why Does My Car Overheat When the AC Is On

Your car may overheat when the AC is on due to additional load on the engine, which can lead to increased temperature if the cooling system is not working effectively. This could be due to a problem with the radiator, a failing water pump, a low coolant level, or a malfunctioning thermostat. If your car is overheating, it’s important to get it checked immediately to prevent major engine damage.

How Long Can My Car Be Parked With the Air Conditioner On and the Engine Running

There isn’t a specific time limit for how long a car can be parked with the AC on and the engine running, but it’s generally not recommended for an extended period. Leaving your car running for long periods can lead to unnecessary fuel consumption, increased engine wear, and potential overheating. Moreover, it can be dangerous due to the risk of carbon monoxide poisoning and is illegal in some areas.

How to Diagnose Car AC Problems

Diagnosing car AC problems can involve checking the refrigerant levels, inspecting the components of the AC system (like the compressor, condenser, expansion valve, and evaporator) for damage or blockages, checking the electrical controls, and looking for leaks. Professional mechanics often use specialized tools and techniques for this process, such as pressure gauges and leak detection kits. If you’re unsure, it’s best to consult a professional.

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