Insufficient refrigerant, huh !! Makes me wonder if the evaporator coil is physically laid out such that the coil region that form the regrigerant exiting area is responsible for these vents while the coil region that form the regrigerant entry area are responsible for the rest. i.e a split evaporator usage.

If this is the case, then you have superheat when the refrigerant is leaving the evaporator which is more than what it ought to be. One clue of this would be the temperature of the low side hose. Is this hose kind of warm where the low side pressure valve is ?

Then just add some more refrigerant till you get low side pressure around 35. You may just need a little more so that the exiting refrigerant from the evaporator is a little cooler.

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Saumil S. Patel