[ElectricBeagle]

When the compressor is off the pressure depends entirely on the temperature and type of refrigerant, as long as there is enough to be saturated, ie. some liquid.

https://www.consulab.com/files/r1234yfPtChart.pdf

Don't mess with it.

 

[ElectricBeagle]

First the coolant/refrigerant doesn't get consumed. So if the BAR reading is low its because refrigerant has leaked out. Refilling AC with a leak I believe is illegal. You must find and repair the leak before refilling.

It is not low, however.