I working on a 02 beetle and the ac is full on freon but the ac clutch wont kick on till i put it at 3000 rpm?

it is a 02 vw beetle i have charged it up so the sytem is full of freon but the compressor clutch will not turn on till the rms hit 3000 i need help with this german car out of 6 year of auto tech i have never seen anything do this