Why Is Car A/C Blowing Fog, Mist, Vapor, or White Smoke? (Explained)

For most people who reside in hot landscapes or drive along hot areas, an Air Conditioner (A/C) in their cars is usually non-negotiable.

You won’t be able to sit comfortably and enjoy your journey until you turn the A/C on first.

However, your comfort may be cut short when your car air conditioner starts blowing mist, fog, vapor, or white smoke.

So, what might be the problem if you turn on your A/C and it starts blowing fog, mist, vapor, or white smoke?

Well, you don’t have to worry much since this article will give you a solved and explained answer as to why your air conditioner is having such problems. So, stay tuned as we dive into it.

Here’s Why Your Car Air Conditioner Is Blowing Fog, Mist, Vapor, or White Smoke

Your air conditioner might be blowing fog, mist, vapor, or white smoke because cold, dry air collides with warm air causing air conditioner condensation. Also, clogged A/C drain holes and overheating of your air conditioner unit can be among the causes.

Car vents
Car vents blowing fog, mist, vapor, or white smoke

Below is an explanation for each cause. Take a look.

Cold Dry Air Hits Warm Air

You will see white fog, especially when the cold air hits warm, highly humid air.

For example, when you step out on a cold day, your breath is quite clear.

Usually, warm air collides with cold, dry air leading to condensation. Eventually, it can be seen as mist or white smoke.

In our case, when you see such on your A/C, the reason might be that your system isn’t getting enough airflow. You must set your air conditioner high for your car to cool quickly.

Air Conditioner Condensation

There might be a likelihood that the mist or smoke your A/C is blowing doesn’t imply that the system is terrible.

It may just be condensation taking place. Especially if you notice the white smoke doesn’t have a bad smell.

You have to understand your A/C usually draws warm air, which eventually cools. As a result, it leads to condensation.   

So, when your heater box has condensation build-up, it can change into vapor and exit from the vents with the cooled air.

Eventually, you will see mist or fog rising from your air conditioner.

Additionally, a clogged drain line may lead to extreme moisture in the heater box.

Clogged Air Conditioner Drain Hole

For older air conditioners, you may have seen drain holes compared to new models.

The air conditioner’s evaporator usually causes condensation when warm or hot air is cooling. In the end, you must drain the condensed water. Your air conditioner is usually made with a condensate drain line where water can drain properly outside.

The drain line’s prolonged use may get clogged, causing water to go back to your air conditioner. You will see white smoke, vapor, or even mist if the drain line remains clogged.

Air Conditioner System Failure

Many car owners have their air conditioners turned on because of the comfort they bring inside their cars.

However, these air conditioners must work excessively to bring cool air during summer. This can put a strain on them leading to failure.

It’s natural for your system to fail, especially if it has served you for an extended period. Commonly when it has failed, you will see smoke or fog if your cooling system has a belt-driven fan.

Another possible reason for your A/C blowing fog or mist is that it might be your motor fan is burned out.

Once you see the vent emitting smoke with a foul odor, switch off the air conditioner immediately. It can be harmful smoke. Make sure you contact an experienced HVAC to diagnose the problem.

Overheating Your A/C Unit

Your AC unit comprises several electrical parts that may overheat, especially when there is inadequate airflow to the system. It can even be severe when the white smoke smells unpleasant or unusual.

In addition, your system overheating can result from blocked vents or clogged air filters. Once you notice this, switch off the system and seek help.

Electrical Problems

A wiring problem can be behind the mist, fog, and vapor coming out of the car’s air conditioning system. Your cooling system has many electrical connections and wires.

If a single wire malfunctions or gets damaged, you may see smoke alongside a foul odor coming out of the AC.


Is it Normal to Get Fog, Mist, Vapor, or White Smoke from Car A/C?

car vent opened
car vent opened

It is usually normal but not all the time. Especially if you see a dirty sock or an unpleasant smell and the mist or fog does not disappear after some time, then you should call a professional to examine your system. However, Sometimes, if you see fog, mist, vapor, and smoke from the AC, it doesn’t mean your system is flawed.

Usually, the mist is the condensed water that develops when humid, warm air collides with cold, dry air. After some time, the mist and fog usually disappear, but if it doesn’t, you can look for help from a professional.

You are entirely safe if you don’t get any smelly mist fog, but it is not normal if you smell an odor like burnt wire due to mechanical corrosion or anything else. Always call an expert if you sense anything unusual with your A/C.

How to Prevent Fog, Mist, Vapor or White Smoke from Coming Out of the Vent

If you are tired of seeing your A/C blowing fog, mist, vapor, and white smoke, try to do the following;

Replace the Filter Regularly

Replacing the air conditioner filter is usually cheap and easy. It will help prevent mist or fog and enhance the air quality inside your car.

Examining and replacing your filter can be done after every three months. It’s always a good idea to examine it more regularly, primarily if you reside in an area with poor air quality.

It is easy to notice if your air conditioner’s filters are dirty, so once you do so, replace the filter while it’s still early. A professional will assist you with this.

Do Yearly Checkups for the Whole System

Try to locate a local HVAC expert and allow them to carry a checkup on your system yearly. You may even have to plan regular checkups if your air conditioner is older.

Frequent checkups will always show problems early that would have become serious in the future. So, it’s better to deal with them early before your system starts blowing smoke and other things.

Acquire a Well-Sized Air Conditioner

The leading cause of intermittent air is usually an oversized unit. Always ensure your HVAC (Heat, Ventilation, Air Conditioner) technician installs the correct size of air conditioner in your car. This will save you from any problems that may arise, like high section pressure on your A/C.

Avoid Switching Off Your Air Conditioner When Outside of the Car

When you switch off your air conditioner, humidity and temperature usually rise inside your car. Eventually, you will notice fog and mist coming out of the A/C when you switch it back on.

Also, switching off the A/C costs more than just elevating the temperature in your car. So, don’t switch off your A/C when heading out.

Get a Variable-Speed A/C

Many A/C system motors usually operate at different speeds. When buying your A/C, always ensure you select between variable-speed and single-speed units. The single-speed A/C functions at only one speed and turns off when it’s done cooling your car.

On the other hand, a variable-speed unit gives cool air throughout your car once you switch it on. It can change speed to give you more efficient and precise cooling. This unit doesn’t turn off immediately but steadily slows down while cooling your car.

Variable-speed A/C usually operates for an extended period. It also removes humidity in your car and eliminates any chances of vapor or fog when the A/C is on.

Is It Safe to Switch Off A/C and Keep Driving?

Yes, it is safe to switch off A/C and keep driving. Your A/C is just an addition to your car’s engine. Whether you turn it on or off, your car’s engine will still operate smoothly. Not using it often won’t harm you in any way other than just reducing your comfort.

However, if you don’t use your A/C for an extended period, it may lead to adverse effects because of the inactivity.

The seals inside your compressor may end up drying, and moisture may build up, leading to refrigerant leaks, which may make your A/C stop giving cool air.

You can turn on the A/C for at least ten minutes each week to keep it functioning for longer.

How Much Does It Cost to Fix a Car Air Conditioner with Fog, Mist, Vapor, Or Smoke Problems?

Regarding cost, it tends to get higher when you have to buy additional parts like a new sensor, condenser, compressor, or hose. And if your system doesn’t need any replacements, you will still spend more for repair.

The cost depends on the service provider, the repair at hand, and the severity of the issue.


You must familiarize yourself with most of the problems regarding your cooling system. When you notice odorless white smoke, especially if you live around high-humidity areas, don’t get so worried. Give it time to see if it can disappear.

However, if the fog, vapor, or mist is thick, black, and full of odor, it will be wise to turn off the air conditioner and contact a qualified HVAC technician. A few problems may seem not to pose any danger immediately, but later they may make you incur costs.

Also, some A/C problems are usually dangerous and thus should be taken into consideration immediately. Finally, we believe you have found this guide helpful, and you have an idea as to why your air conditioner is blowing fog, mist, vapor, and smoke.


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