Ac system will not take full charge

[John861214]

Hi I'm working on a 02 Dodge Durango with front and rear ac the rear doesn't blow cold the front is cool but not cold as it should be I just replaced compressor expansion valve and dryer under hood vacuum down the system waited a hour it held started to charge with gauges and can of freon got it to take 1.5 lbs but could not get the 2.4 lbs in the system the compressor is running all the time without cycling the condenser fan is working but my pressure readings are 50 low side and 230,240 high side thinking there might be another expansion valve on rear evaporator coil but not sure if I should change it or the pressure switch is bad not cycling the compressor.