Hi all. I haven't been on here for awhile, but it's time to get this a/c issue fixed. I completely rebuilt the a/c front to rear about 6 or so years ago. No issues. Now, another new compressor due to a front seal leak. Recovered pressure nicely, installed new compressor, accumulator and orifice. Those are the only connections opened up, besides moving pressure switch from old accum, etc. At first, would not hold any vac. Obvious leak. But where? Opened each connection again and replaced seals (orings) again just in case, including oring on pressure sw on back of compressor. Now pulls about 5in hg, but no more. Gotta get it to 29 and hold. Are there any really good ways of pressurizing the sys for leak check without freon? Like air or something? Just need to locate this leak and I'll be good. I only know enough about this stuff to be dangerous.