I was doing an AC fireoff a few days ago, got done doing all my brazes and of course used good brazing practices such as wet ragging the service valves on outdoor coil and wet ragging indoor TXV and removing sensing bulb off coil. After this, did my pressure test and nothing seemed out of the ordinary. Slight pressure drop as usual from my lines cooling down after brazing, so it didn't cause any alarm. After that I started the vacuum, it got down under 1000 microns and right when it started to get to around 500 the reading jumped up to 650 then back to around 500 then up to 750 and fluctuated like that. When I isolated my pump, the system was at 750 or so and then climbing. At that point it was late and I had no bubble test or anything to check brazes. Came back a couple days later, hooked my gauges up and the system was still under slight vacuum, approx -11 inHg. Broke vacuum, pressurized system and it was slightly dropping a .1 at a time, very slowly. This time tested all my brazes 3 times with bubble test. All good. Went to pull a vac and my pump sounded like it was struggling to do so, and I couldn't get system below 50k microns. I know it's not my pump because I have used it and my entire set up on other jobs in between this one with no problem. At this point I isolated outdoor and indoor coil and put it under pressure to see if the evap coil is leaking or outdoor unit is leaking past the service valves. Any ideas guys?
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