Air-con units

I have recently bought an air con unit and used it in the summer on a new grow room, i lost 2 or 3 crops in the new grow room and now have through process of elimination got some green growing like wild fire in the room (im not using the water on site). i havent used the air con unit yet but also havent switched all the lights on yet.
so i was wondering if anyone out there uses air con units and if they harm the plants or not (i hear they help bactiria grow)???? thankx