Why is white smoke coming out of the AC vents in my car?

White smoke coming from the AC vent indicates a problem with parts of the engine or the cooling system. It could sometimes be traced in the damaged part of the AC system. Whatever the cause is, it should be taken seriously.

So, why is there smoke coming out of the air vents in my car? Some causes of white smoke from the Ac vent may include engine overheating, low oil level, cooling system issues, high humidity, etc.

White smoke is less harmful as it contains less toxic components. It is because white smoke is mostly caused by excess hot air that finds its way to the heater box, which is then condensed. Then the condensed hot air turns to vapor and finds its way through the AC vent as white vapor.  

The smoke is hard to detect initially because it could come with no smell. It will only be noticed when the white smoke becomes significant in the vehicle.

smoke coming out of vents when ac is on

What are the Reasons white smoke from ac vent car?

There are a lot of issues that could be caused by smoke from the AC vent in a car. Most have to do with any factors affecting the engine’s temperature. For instance, low oil levels, coolant, damage, oil leak, etc.

Other factors could also contribute to white smoke coming from the AC vent in a car. Below are some factors that cause the problem “smoke coming out of vents when ac is on.”

Car overheating

The engine’s cooling system plays a vital role in the working condition of the engine. When the cooling system is damaged, the engine overheats, a large amount of hot air is pulled into the air condition, and condensation is produced. If a large amount of condensation is created in the heater box, it will turn to vapor and escape through the AC vent as white smoke.

If you have been driving nonstop daily without paying attention to the water level or coolant, there is a high probability that the engine will overheat. When this happens, the engine’s internal components and the vehicle’s other parts will also heat up, causing white smoke to come out of the AC vent.

Low oil level

Your vehicle’s oil level is one of the major causes of overheating. Suppose you are a person who uses the AC frequently and does not pay attention to the engine oil level. In that case, there is a high probability that the internal components will heat up, resulting in hot air which gets to the AC system, and then the hot air is condensed and could escape through the AC vent as white smoke.

When the oil level is low, the engine’s moving parts struggle, increasing friction. As a result of these, the heat coming from the engine will also increase and find its way to the AC system.

Worn-out components

Worn-out components of the engine or other components of the cooling system, like the fan motor, a lot of heat or heat gets into the AC system. As explained earlier, the hot air could result in white smoke from the AC vent.

As time goes on, the parts of the cooling system will begin to wear out and fail; when this happens, heat in the engine will start to build up due to the failing cooling system.

Once the cooling system does not function, more hot air will be drawn into the AC and cooled, resulting in condensation. Once too much, the condensed air will escape through the AC vent as white fog or smoke.

Heater overuse

If you use the heater too often, the core can get damaged, and a leak can occur through the damage. The heater core can be located in the dash, and a small radiator collects hot coolants.

When the heater core is damaged, coolant will flow into the engine, which will cause it to be burned there, and white smoke is created. It causes the problem of coolant smoke coming out of vents. As this happens, white smoke is created and drawn back into the AC and escapes through the vent.

Oil leak

If there is an issue with the oil reserve cap or a leak in the reserve, then oil will escape to parts of the engine if it is not wanted. Due to the heat generated by the engine, the oil will get burnt in those areas and then create a white fume, which could get to the AC vent.

White fumes caused by oil leaks come with a very bad and suffocating smell, making it very difficult for people to enjoy the drive.

High humidity

If the humidity around the AC is lesser than in other parts of the vehicle, fog-like smoke will be created and come out from the AC vent. The fog is different from smoke, and it causes smoke coming out of car vents no smell as it does not come with a burning smell like leaking oil. It is rather cold and pleasant.

Clogged drain hole

Older vehicles have a drain hole used to drain condensed water from the system. Once the drain hole gets clogged, the water will accumulate to a certain level. It will then evaporate within the AC and escape through the vent as white smoke.

Issues with the compressor clutch

If the compressor is seized, the belt will cause a lot of friction whenever the clutch is engaged, causing it to smoke up. The AC can also draw white smoke from the damaged compressor to the vent.

white smoke coming from ac vent in car

What to do if white smoke from ac vent car?

Many components could cause the white smoke from the AC vent in the car, which is why it could be difficult to troubleshoot the problem. However, knowing the possible causes, will give you an idea of how to fix white smoke from Ac vent.

The first thing you should do when faced with a problem like this is check the vehicle’s temperature. If the car is overheating, the cause of the issue could easily be narrowed down to factors like low oil, oil leaks, low coolants, and cooling system issues.  

Below is what you could do once you encounter white smoke from the AC vent.

Check and top up engine oil.

If the engine is overheating, the engine is not receiving enough engine oil, causing internal components to generate a lot of heat and smoke. In such a case, park the vehicle and allow it to cool down well enough.

Once the engine is cool, check the oil level using the oil dipstick. Once you notice the oil level is low, top it up immediately.

Also, ensure that after adding the oil, there is no leak. You can do this by observing beneath the vehicle for oil on the floor. If any is found, trace the leak to its source and have it fixed.

Fix worn-out components of the engine.

The engine and cooling system is a complex system comprising numerous parts, making it very difficult to troubleshoot the issue without proper mechanical knowledge. We advise that if a damaged engine internal part causes the smell, take the vehicle to an expert.

Replace the damaged filter cap and the filter.

If you notice that oil is dripping from the position of the oil filter, it means that the cap was not fixed properly or is damaged. To solve this problem, you first need to drain the oil before taking off the filter cap.

Once the oil is drained, take off the oil filter cap and examine it. If there is any obvious damage to the cap, replace it immediately.

Also, the oil filter cap leak could result from a clogged or dirty filter. A clogged filter will limit or stop the oil flow, forcing it through the oil cap. If this is the cause, you need to change the oil filter.

Replace the compressor clutch.

If the cause of the white smoke is damage to the compressor clutch, then you need to have the clutch replaced as soon as possible.  You can find the compressor clutch at the front of the compressor, which is connected to the engine by a belt.

Sometimes, the belt could be the issue; it could move out of position or completely break. Check the belt if out of position; fix it. However, if the belt is broken or damaged in any way, have it replaced.

Replace the damaged heater core.

The heater core is a small radiator that can be found under a vehicle’s dashboard. It is between the instrumental panel and the firewall. You can also use the owner’s manual for more understanding of the location of the heater.

Check for leaks or significant damages once the heater core is located. If any is found, replace the heater core with a new one.

Change the air filter.

If the smoke coming out of the AC vent results from humidity around the AC vent, then the cause can be traced to a dirty air filter.

The air filter is located under the hood in the cold air collector box close to the front part of the engine compartment. Replacing the air filter is straightforward.

Read Also: How Often To Change Cabin Air Filter?

What type of smoke can come through the AC vent?

Three types of smoke could come through the AC vent: white, black, blue, and gray. The color of the smoke from the AC vent shows the engine’s condition and what may cause the issue.

White smoke

White smoke is a less harmful type of smoke from the AC vent. In most cases, the smoke does not smell and may be hard to notice initially. However, the smoke becomes more significant and visible as time passes, filling up the car space.

Black smoke

The black smoke is majorly caused by something burning in the car or internal components of the engine. When this happens, the black smoke fills the vehicle’s space, entering through the AC vent.

Black smoke can be very toxic as it is packed with dangerous substances. It is easy to notice because of the burning smell and visible color. Once you see the smoke, pack the vehicle and ensure to have the issue fixed.

Gray smoke

It is also a less toxic kind of smoke; unlike black smoke, it is hard to notice. It is similar to the white smoke and may have similar causes.

Blue smoke

When there is blue smoke, it shows that there may be an oil leak in the car that has found its way into the engine. An issue like this needs to be fixed immediately to avoid engine failure.

Read Also: Why is My Car Air Conditioner Not Blowing Cold Air?

How much does it cost to fix the problems?

There is no general cost for fixing white smoke from an AC vent; the cost solely depends on the cause of the problem. For instance, if the cost of the smoke is a damaged heater core, the price will range from $800 to $1,000, including labor costs.

In addition, if the cause of the smoke is clogged air filters, the filter needs to be changed. It will cost between $20 and $50, excluding the labor. Depending on the mechanic, labor costs could range from $50 to $100.

Depending on various factors, the compressor clutch replacement cost will range from $500 to $700. The labor cost would be around $200 and could go higher depending on the mechanic.

Final Words

It is important to pay attention to the smoke that comes out of the AC vent of your vehicle. Different types of smoke can come out of the AC vent and come in different colors. Once you see any unusual smoke coming from the AC vent, you need to have the vehicle checked. It could be a serious engine issue, and acting fast could save you from spending a lot of money on engine repair.

Akindayini Temiloluwa

I am passionate about everything automotive. Right from when I got my first toy car as a kid, I developed an interest in the inner workings of vehicles. As I grew up, my love for mechanical stuff became more substantial enough for me to pursue a career in it. 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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