I think you are supposed to remove the schrader valve before you install the r-134a quick-disconnect fitting. That's what I did when I converted one of my Mercedes. One alternative is to use a tool that allows you to change the schrader (r-12) valve without evacuating the system. You see them for sale on ebay occassionally for around $45-$50. I bought one on ebay because I also had a bad schrader valve, but have since sold my car with r-12. I was going to resell it on ebay, but if you would like the tool I'll sell it to you for $40. It was only used once, and its a lot easier and cheaper than paying someone to evacuate the a/c and do the repair.

FYI, evacuating the refrigerant takes oil out of the system as well. A good a/c mechanic will measure the amount of oil that came out (via the oil-trap in the evacuating machine) and put that much back in when they charge the system. Good luck finding someone who will do the job that thoroughly.

Let me know. [email protected].

GregS