Sometimes the moisture can build up because a drain is clogged. A technician can clean that out and get things draining again. If the vapor coming out of the vents has a sweet, syrupy smell, it could be caused by a hole in your heater core. The heater core is the part that helps heat the cabin in colder weather.
The odorless, white steam or smoke coming out of your air conditioner is probably excess water stored in the heater box . Commonly, it is a sign of a restricted drain hole that needs cleaning. The steam or vapor collected during the process of condensation could have made its way out when the air hit it.
The cause of sweating vents is simple. Air that's humid enough finds a surface cold enough. When vents start beading up with water--or worse, dripping--either the humidity is too high or the vent is too cold. It's not hard to figure out which of those two is the culprit. Just find the dew point of your indoor air.
Don't worry—it usually doesn't mean there's something wrong with your air conditioner. The mist is just condensed water vapor that forms when cold, dry air comes into contact with humid, warm air (we'll explain this in more detail later on). Usually, the mist will go away on its own after a minute or two.
The purpose of the drain hole in air conditioners is to allow condensation to escape. However, over time, dust and debris can build up causing a blockage. This leads to backed-up condensation in the air conditioner which then gets released as a mist or fog from the AC vents.
Without prompt attention, excess condensation could overwhelm your air conditioner's drainage system, causing damage within your home. This damage can range from high humidity levels that lead to mold and mildew proliferation and spots, to structural damage from drainage water that accumulates and puddles.
“The odorless steam coming from the vent is possibly excess water accumulating in the heater box, which may indicate the drain hole is restricted and needing cleaned.” Dave Carney, president of Hillside Auto Repair in Torrance, said the problem usually occurs in older cars.
As the hot refrigerant circulates through the condenser and releases its heat, moisture from the surrounding air condenses on the surface of the condenser coils.
The AC Condenser Coils Need to Be Cleaned
Over time, these coils can become clogged with dirt, dust, debris, plant matter, and more. This build-up of contaminants can prevent the coils from doing their job properly, resulting in humid air being blown into your home instead of cool and dry air.
A drip or two of water leaking from under your car is normal, but if it is increasing in frequency and volume, your car needs to be checked.
If the air temperature near the appliance is below the dew point, this causes water vapor to form in the air and condense into water droplets, thus causing the fog or smoke. A dirty air filter or low fan speed may aggravate the condition.
A warning sign that your car's condensate drain might be blocked is when you notice the water leaking inside your vehicle. If you find your car's floor getting wet with water whenever you turn your car's air conditioner on, then it's time to check your condensate drain.
Answer: Vapor or mist coming out of the AC vents in your car is usually just the result of water condensation. As long as it's not accompanied by a strange smell—like the sweet fumes of engine coolant—you likely have nothing to worry about. The air conditioner in your car cools the air by removing heat and moisture.
When your car sits outside, especially overnight, condensation can build up inside of the exhaust system. Starting your car will warm that condensation, turning it into steam. As the exhaust system warms up, the condensation will disappear, and the white steam along with it.
The air conditioner draws warm air, which is then cooled. This naturally results in condensation. If the heater box has condensation buildup, the condensation can turn into vapor and go out of the vents with the cooled air. As a result, you'll see white fog or “smoke” coming out of the AC vents.
Sometimes it can be caused by water accumulating in the vent system after it condenses. That water can wind up at the bottom of a vent, and when you turn on the blower motor, it can cause what looks like steam or vapor to come out of the vents.
The air conditioner's cooling cycle includes pulling in warm air that is then cooled. As a result of this process, condensation is produced. When moisture builds up in the heater box, it may eventually turn into vapor and get released with the cooled air, so you see white smoke coming from the air conditioner vents.
Condensation resulting in water puddles under your car is perfectly normal, but sometimes this water can escape into the car's interior. This signifies a bigger problem.
Specifically, the evaporator core leaks water from under the passenger side of the engine compartment when the air conditioner is being used. This is normal use. Coolant: if the liquid smells sweet and appears to be tinted or colored (yellow/green), it could be coolant.