Rans

I have a 2001. My a/c freezes up and the air blowing out the vents gradually decreases untill there is very little air coming out of the vents, even tho the fan is still running on high. The compressor is not cycling on and off, just staying on. Does the 01 have a low pressure switch to cycle the compressor or does it have the variable stroke compressor that is supposed to run all the time the a/c is on?
It will run about 40 mins. before it starts freezing up. Any help would be greatly appreciated.
Thanks,
Rans