aircon making car rev

[blackers10]

hey guys
i had my aircon on yesterday on the way to the all ford day and was talking to my dad about how my car every say 20 seconds or so i hear a CLICK like a solinoid going from under the bonnet and then the engine revs up 100rpm or so then goes back down (sorta like a light blip on the throttle)
its always done it.. and only when the A/C is on

also water drips on the passenger side foot well while hte A/C is on??

is the 1st issue normal?
and how do i clean the water overflow tube to stop my floor getting wet?

thanks guys