Nissan Repair: nissan bluebird/stanza ac problem, nissan bluebird, expansion valve

Question
Im currently bringing back to life my 92 nissan bluebird and the other day i had my ac fix at a local shop, they replaced the drier cleaned the whole entire system and replaced the freon and upon checking the system I notice the compressor wasn't shutting off automatically I have to do it manually at the button. Now my ? is there a sensor  that I could replace myself or is't in the compressor it self? thanks in advance

Answer
Eddie,

The expansion valve is in the blower case where the evaporator is.  Most likely, it is stuck.  You could drive it for a time and see if the compressor begins to cycle.  As in a couple of days.  Otherwise, the expansion valve will have to be replaced.  That means discharging and recharging the system again.