To be certain:
* Consult your owner's manual: This is the best source for the exact location.
* Look for a smaller, usually capped fitting near the AC lines: The lines are usually metal and relatively thick. The low-pressure port will be smaller than the high-pressure port.
* Use a diagram: A diagram specific to your 2000 Ford Ranger's AC system will clearly show the location of the low-pressure port. You can often find these online by searching for "[Year] [Make] [Model] AC System Diagram."
Important Note: Working with automotive AC systems involves handling refrigerants that can be harmful. If you are not experienced with AC system maintenance, it's best to take your vehicle to a qualified mechanic. Improper handling of refrigerants can lead to injury or environmental damage.