Many shops use shop compressed air but the better ones will use nitrogen. Pressurize the system and then go around with a solution of soapy water on all of the joints. Listen for hissing at the compresser and it is not uncommon for a hose to rupture internaly. Check the input fitting of the condenser coil ( the one in front) Do not run the system without freon. After finding and fixing the leak you must replace the dryer and evacuate the system for at least 1/2 hour. I recommend refilling with R-12. Many of the "drop-in" replacements have propane or butane in them and you can imagine the excitement you will have if you have a leak and it should ignite.Although R-12 is expensive replacing it won't cost that much more considering all of the other work that will need to be done.At about $20 a pound you only need less than 3 pounds. David Teitelbaum vin 10757 --- In dmcnews@xxxxxxxxxxx, "Steve Rubano" <srubano@xxxx> wrote: > Hi all, I was wondering if someone out there with A/C system > knowledge can give me some advice. The A/C system on my car has > been "dry" for some time now (don't know how long) where as all the > freon was out. I am assuming there is a leak somewhere. There was no > hint of pressure at all when I was taking it apart. Here are my > questions: > > 1. What should I suspect/check on my system that would go bad from it > being dry for some time now? > > 2. Is the new "legal" freon as cold as the old stuff? I have only > dealt with the older stuff so I can't compare the two. > > 3. Can I check for leaks in the system without charging it with > freon? I know that there are special UV Dyes out there you can inject > into the system and use a black light to track the leak. Can I use > this without charging the system or do I have to charge it so I can > run the A/C to find the leak? > > Any info would be appreciated, thanks. > > Steve