'86 300E - A/C - Hot air in rain

[pjavier_garcia]

Well, to re-iterate, it's an '86 300E and I noticed once that when I hit a puddle at high speed and the water went up into the engine all of the sudden the A/C would only blow hot air. I also noticed that during a rainstorm the same thing happened, as soon as the car got wet the A/C started to blow hot air. Well I'm not too well versed as a mechanic but it seems as odd behavior to me, so if anyone could shed some light as to why this is happening and what I could do to prevent this, I would greatly appreciate it. Thanx in advance.