HELP WITH A/C problem
 

I have a 2001 beetle I just purchased put new compressor, condessor,dryer the works Charged a/c also put oil in it an Heres the thing It doesn't kick on till you Rev it up till about 1500 or more.. When it engauges the first time compressor stays on for about 4 secounds then cuts off for a sec then right back on an gets shorter an shorter Then after fourth Kick on it starts kicking on an off for about a second each time so forth But only kicks on when the car is rev up. I have checked to make sure it has proper freon in it. Oh other thing is when it's kicking in an off it's starting to cool down the inside so system seems to be working on the cooling side.. I posted this on other websites an no luck yet either