Serpentine belt chirpin'

[6.slow]

Wondering if anyone else has this, When it's raining, I hear a "chirp" like a belt slipping for half a second. Only happens when I have the fan on. Is this normal or am I gonna have to start saving for repairs? It happens about every 20-30 seconds and is getting worse. I have removed the front airdam a couple of times and wonder if I put it back wrong and wwater is splashing up into the engine bay. And, there is these rubber flaps just behind the front bumper, I don't know what way they are supposed to go... Above the bumper or down. Hard to explain, but from under the truck, or with the front fasica off, it''s easier to see. Any help would be good help. Trucks all stock 'cept some knobbers under the fenders.