air condition problem 93 century

my 93 century air conditioning will freeze you out for about 15minutes ,then its starts blowing less and less.the entire system is froz solid.any ideas?

Check to make sure that the drain for the evaporator is open. Usually the issue is due to condensation on the evaporator core and will cause it to freeze. The drain should be located on the firewall on the passenger side of teh vehicle.