What Now?

We have an '85 3L Extended cab Ranger. Last year our A/C compressor packed up but I was able to get an identical one from a Mustang. Well, identical physical dimensions. Having replaced it, I lost the complete refrigerant charge, of course.

My questions are:

1. What would be the best "over the counter" refrigerant to use? One store sells Red Tek 12a.

2. After losing my complete charge, would I have to consider adding oil to the system now?

3. Do I have to create some vacuum before attempting to fill the system?

4. Lastly, should I do a pressure check to see if it's going to hold gas before buying some and how would I do this.

Thanks very much for any help or references to previous threads.

What Now?