Hi. I'm doing my AC ticket(2nd year) and need a little advice. I have the pump pulling a vacuum overnight on the unit. The micron gauge had pulled down to about 1000 microns before i left it for the night...so there doesn't appear to be any leaks in the system. When i go to charge the unit tomorrow...providing that the vacuum holds good(~500 microns)....my question is what to turn on and/or not to...when charging. Should i charge a bit into the low side first before turning the unit on? ....or should i turn the unit(compressor) on first, then open the low side on the manifold? Is it safe to run a compressor in vacuum before you start to charge? Thanks!