Subaru, air conditioning, variable, Displacement, compressor controls, low side and high side PSI 

Old guys using cans of refrigerant, who were taught to raise the rpm of the engine so they can add refrigerant until they see a certain pressure that they “THINK” 🤔 is correct . ITS NOT !!!…
As you’re raising the RPMs because the old time technician with no knowledge doesn’t know that the computer is taking over keeping the high side pressure down the low side pressure up as he keeps adding refrigerant. The computer keeps trying to re-correct the pressures to what it thinks, it should be not knowing an idiot is holding a can of refrigerant, force-feeding it too much refrigerant .