bridluz

Brought my C55 in for an AC check, they tested it and put freon in and it blows cold. Weeks go by and infrequently my ac wont blow cold. Which in the rain and humidity of Houston means my front window fogs up like crazy. So I brought it back in to the shop and the freon is fine, no codes show up, air blows cold for the shop.
Starting to maybe put 2 and 2 together I was out, started raining and she wont blow cold again. So, it seems as though something is getting wet causing the ac to not blow cold.

Any ideas greatly appreciated before I bring her back to the shop?

Supgee

That's interesting, as the A/C system is sealed and water intrusion is not really a possibility since you said the system holds freon. If water could enter, then freon could escape and the system would never get cold.
It's possible that the water is getting onto one of the sensors for the A/C system and corroding the connection (refrigerant pressure sensor, evaporator temp sensor, etc). Could be that one sensor stops functioning and causing the compressor to turn off.

Have your shop spray the car with a pressure washer all around the front/condenser,etc and see if they can duplicate it.
edit: also make sure they have a star diagnosis, and can read out the actual values for the A/C system while they are trying this... then they can see what(if any) sensors are malfunctioning.