where is the a/c orifice tube

This orifice tube is located inside the liquid line that runs from the condenser to the evaporator.

You will need to pull the system down and evacuate it in order to open the system to replace it. Here is a guide that will help with this:

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

Below you will find all the detail on where this line is so that you can replace this orifice tube. It is number 4 in the last attachment.

Please run through this and let us know what questions you have. Thanks