Can I ask for where is that in the engine compartment?
For my 2003, the A/C compressor, and therefore most of its plumbing, is located at the very bottom of the engine compartment. So it is pretty difficult to follow the "piping" and thus to ID the components of the system (like which of the cylinders is the accumulator).
There appears to be two service ports. At least from what I can find. One located right next to the passenger side strut tower brace, and another is located right next to where the upper radiator hose enters the radiator itself.
There are caps on both of them, but neither has any markings to ID its purpose. All that is on the caps, it he name of the manufacturer of the cap, and its thread size.
Which one of those two ports I found, is the low pressure service port? Can anyone help?
EDIT:
Here is a pic (not my Mustang though), with yellow arrows pointing to the two ports I found...
View attachment 383011