Chevrolet Repair: ac problem, autozone, side vents

Question
on a 1997 silverado was having problem with amount of air through face vents a lot of noise but low volume. was going to replace blend door actuator but on way to autozone completly stopped blowing to vents ,except to little side vents to door glass. Now compressor will only engage when compressor switch is in OFF position, when you engage switch, light goes off as well as compressor. Would low pressure switch cause this?

Answer
GOOD DAY ALAN, NO LOW PRESS SWITCH WOULD NOT CAUSE YOUR PROBLEM. THIS SOUNDS LIKE THE PANEL CONTROL HEAD IS FAULTY..YOU ARE SAYING THAT THE COMPRESSOR WILL TURN ON WHEN THE CONTROL SWITCH IS OFF. LOW PRESS SWITCH WOULD TURN THE COMPRESSOR OFF IF THE FREON WAS LOW. THIS PROTECTS THE COMPRESSOR FROM RUNNING WITH LOW FREON...I WOULD TAKE THE CONTROL HEAD OUT AND CK FOR POWER COMING OUT OF THE SWITCH,I THINK YOU WILL FIND IT IS FAULTY.. THIS CONTROL HEAD ALSO CONTROLS THE BLEND DOOR ACTUATORS AS WELL..I HOPE THIS HELPS YOU AND GOOD LUCK,,TOM