Hey a/c pro's out there. Im just getting into doing ac as part of my job. There is no one at my shop that knows anything about a/c so I am researching and reading stuff on my own to trying and teach myself. Maybe you guys/gals can give me some pointers/tips. I do not have the all in one unit, i have individual tools. I have a recovery unit, vac pump, manifold, scale, and die kit. I have also purchased a 2oz oil injector. I guess my first question is when I ad the oil with the injector, how do i know when it is all gone from the cylinder? It is the silver canister with the hose on one end and you hook the low side from the manifold to the other side. I have been hooking it up and shutting of my low side on the manifold while the vac is running and then removing the cap off the injector cylinder. The vac on the high side sucks it in but i have to have the cap removed to know when it is gone. Is this what ya do?? Also, if you do not have a spec on how much refrigerant you need what rule of thumb do you use? Just keep adding till the high side reads double ambient temp is what i have read (with 134a)? Hmmm.... 1 other thing. You know how the gauges cycle when the pump kicks on and off? At what time do you take you low side reading? Most of the stuff I have been hooking up to has a range of 10psi to 50psi on the low side while it is cycling. Any tips would be appreciated!!