AC Repair Question

[brycraft]

I have a question regarding a 5 year old American Standard Allegiance 10 Central air unit. It is the 2 ton model. My sister in law just moved into her home and found the a/c was blowing warm air so a repair person came out and cerviced the unit with freon and told her he repaired a leak but couldn't guarantee it would last, charge $300, well it didn't hold and he came back, charge her another $50 and told her she needed a "NEW SERVICE VALVE ON THE CONDENSOR" that he couldn't repair it and it needed replacement cost about $600 because it is in a difficult location because of lines and what not. First does this sound reasonable? second can a non service person purchase this part on his own (like myself)? and where could I locate this part? I am a licensed aircraft mechanic with a high degree of mechanical aptitude and if this is somthing that can be done I would rather do it myself then have her pay more money that she can't afford. If it came to it is she throwing money away at this particular unit and should she consider a whole new unit like an Amana or Carrier?
Thanks for all your help

[LazyPup]

To answer the second part of your question, the anwer is simply NO. In order to change a valve on the refrigerant system you would have to first pump all the refrigerant out of the system. Current Federal EPA regulations prohibit anyone, possessing, transporting or dispensing refrigerants unless they are a certified refrigerant handler, have met all the requirements of training as set forth by the EPA. In addition, you have to have an EPA certified recovery machine to pump the refrigerant out. (recovery machines range from $800 to $2500). Actually your technician did you a favor. EPA regulations prohibit installing refrigerant into a system with a known leak. To be in full compliance with the law he should have either pumped the system down, made the repair, then charged the system, or if the customer refused to pay the repair cost, by law he was required to either pump it down, or notify the EPA in writing that the leak exists.