This morning after a cold start, driving for about 3 minutes, i merged onto the freeway, and after getting up to speed steam started coming out of my vents. Not very much, but enough to go, "whoa whats going on?!?!?!?" .I turned the vents onto max for a few seconds and it stopped.

Its been raining like crazy here....could it have just been water vapour evaporating or something? It didn't happen again after I blew the vents out.

 

I believe you have discovered a facet of condensation.
The cold condensed air from the AC is mixing with the water vapor rich air in the truck and cooling it to a point of physical phase change.

 

That could be the problem.


BTW, FU. You have rain.

*edit*
BamaRamninjaedit!

 

If it smells sweet like antifreeze it could be a heater core leak, otherwise drive on.

 

What he said, except drive it like you stole it!