Dash Vents Mist

If a customer complains of mist coming from the A/C vents when the air conditioning system is operating, most likely, it is a normal condition caused by many factors and should not be considered a problem.

The reason the mist is coming from the vents is because the evaporator is operating close to or at the freezing point and may even have a little ice on the fins but not enough to affect its operation. The outside air is probably very humid, perhaps 85Z to 95Z. When this very humid air comes in contact with the cold evaporator, it causes the moisture in the air to condense into a mist. You have probably observed a similar situation when you opened the freezer on the refrigerator at home. This mist is then pushed through the vehicle's ducts by the fan and into the passenger compartment.

To correct the situation is simple. Since we can't change the weather conditions, we have to make a very minor adjustment to the vehicle's air conditioning system. That adjustment is to move the temperature lever on the control panel slightly toward the warm position. All we want to do is blend a little of the warm air in the heater core with the outside air to melt the coating of ice on the evaporator. The cooling of the vehicle will not be affected since we are only moving the temperature lever very little. The customer will have to experiment to find the position that cures the condition as it can change based on the weather conditions mentioned above. If there is little or no humidity in your area, you will probably not be faced with this problem since it is the humidity that generally causes this complaint.

So if you have checked out the vehicle and can find nothing wrong, perhaps the weather is the cause of the problem and a few minutes explaining this to the customer will make you happy and they'll keep their cool.