Question:  Where is the orifice tube located on a 1990 Cadillac Deville?

Answer:  On the 1990 Cadillac DeVille, look near the firewall on the passenger side.  The orifice tube is located in the liquid line, at the evaporator inlet.  The photo below shows the inlet and outlet tubes.  The liquid line (inlet) is the smaller of the two tubes connected to the evaporator.

FYI:  An orifice tube in a properly functioning system can be found by locating the area between the outlet of the condenser and the inlet of the evaporator that suddenly makes the change from hot to cold. In some cases you'll see small indentions or dimples placed in the line that keep the orifice tube from moving.