... just some added refrigeration info..
There are two sides to a refrig loop.. low side/high side...
When compressor is running , the seperation points of the two sides are at the compressor [ internally , between suction/pressure ] and whatever type metering device is used [ Expansion valve, cap tube. POA valve, etc]
Anything from the compressor pressure to the metering valve is referred to as the high side and anything between the metering component and suction port back at compressor is the low side.
All pressure are equalized when the unit is not being used , but when the compressor is on, the high side will be more pressure than a dormant unit and the low side will be less.
Many hard to find high side leaks can only be found when the high side is pressurized b/c the are more likely to leak at the higher pressures of a running unit, whereas an evap leak is more likely to leak sitting dormant as the equalized pressure of a charged unit is higher in the evap [ low side] than when unit is running.
When looking for an evap leak, some techs will roll up the windows , close the doors and let the car sit overnight [ charged w/refrigerant]. The next morning they will stick a sniffer up into the evap drain holes .. the refrig. is heavier than air , so it tends to settle at the lowest point and can be detected.
Same technique is used by commercial refrig techs....they always snif the floor of a unit that is suspect of evap leaks.