Let me correct you. The standard filling process of any car is charging the liquid with the cylinder upside down and low side or high side has nothing to with the liquid.
Few cars have a procedure mentioned on the bulk head garnish, replenish with 100g +- 25g, however the workshop manual states 400+- 25g so in this type of state you add 100g of refrigerant first, and then tilt the cylinder upside down on the same weight scale you have charged 100g of liquid. And rest 300g of gaseous form.
If you don't do this the ac system would start tripping on 14degrees on vent and won't go any lower.
But 90% of vehicles don't require gaseous vapours, they directly need liquid charging. And in short refrigerant is basically in liquid form in most of the vehicle . Whenever you purge it in air it gives a white cloud. And freezes your hand to frost bite for secs. So you've to stick to standard filling procedure of your car.
And civic standard procedure is cylinder should be upside down and only liquid will go inside.
So it could be many things I can't comment without seeing the vehicle.
How your ac performs is a step cycle.
Compressed heated Discharge goes to condenser
Condensation occurs liquid flow is pushed to the ac drier with desiccants in it to dampen the moisture if present,
This process also cools the temperature of refrigerant. Then it is pushed to the Txv, where it sprays it in the evaporator, this makes the evaporator frozen to negative degrees and blower is sucking or throwing air across in to ducts to our vents. And on the other hand suction is coming in action of a compressor sucking in gaseous sprayed refrigerant + liquid in some capacity with oil again going in the loop.
So discharge to Txv is all high side
And Txv to compressor is suction side. (here is where we add refrigerant) so you can't deny that liquid refrigerant is not to be added....
So In short you follow the workshop manuals and learn from there and don't just do random practises.
Mostly ac technicians are like oh sir jeee humara roz ka kaam hai and they screw your car. So always go for logics. Like in this case if two people have said switch, then you should ask them how did you reach to this conclusion that it's a bad solenoid switch.