greetings, boy starting on this and it will be the first time that boy to load mp39 to replace r12, my doubt is how it is loaded in liquid or gas, and if it is high or low and as appropriate, in advance, thanks.

As it is charged in liquid phase, with an inverted carafe, you can load by weight or little by little, for me it is better little by little, taking care of the condenser heating, the amperage of the compressor, the pressure on the low side and the Uniform frosting of the evaporator or coil, you do it by the service valve, greetings and luck.