1996 Nissan Altima ac problem

I have a 1996 altima gxe the ac compressor clutch works engages when car is cool then shuts off about 10 mins later It has been coverted to 134a. dont know if it was evacuated properly, just bought car.It has enough 134a it blows cold as long as clutch is engaged. should the the condenser fan come on even when engine is cold.however both fans were running when i looked at it.I installed a new high pressure switch what else could it be?