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Smoking AC Vents

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I have a 2005 Legacy GT with 70K Miles on it.

Yesterday I took a trip to the beach and to do so had to go through a long underground tunnel. I had already been driving for 1 1/2 hours on the highway with the AC on. Which brings me to my issue. As I was passing through the tunnel I put my windows down it was vey hot and muggy inside the tunnel and so at the end of it I put my windows back up and turned the AC on. As soon as I did this white fog came out of the AC vents then quickly dissapated only leaving some water condensation on the vents. The fog coming out had no smell and looked the slightest bit white. After that I drove another 5 hours with the ac on and nothing happenned again today it is fine. There is no excess water under my car and no water leaking into the cabin.

My question is, could it just be from the tunnels hot muggy aire meeting the dry cool air causing condensation or could it be something as bad as a heating coil?


Thank you!

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Used to happen more with R12 systems that worked better than R134a. It's the same effect as breathing out in winter. Hot humid air meets cold dry air, the hot air is cooled to a point where the moisture briefly condenses into water vapor before evaporating again when it's warmed up by the ambient temp in he car.


110DegF hot humid air from outside -> Cooled to ~40DegF causing the moisture to condense -> Warmed up to ~75DegF in the cabin causing the condensed water to evaporate again.


First time I saw this I thought my car was on fire!

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