Diagram on panel is not legible. Trying to figure out if the solenoid valve on the liquid line is stock. I cant for the life of me see its purpose. I should have taken a pic but ill do my best to explain in words, something I lack greatly in.

The distributor tubes come out of the condenser and into the distributor head and then screws on to the liquid line(i have a 10deg temp drop across this assembly which Im pretty sure I shouldnt have) which goes into the evaporator distributor assembly. The solenoid is not in-line on that liquid line. How do I word this.....ok...say you installed two T's in a liquid line about 6 inches apart. Into these two T's they have piped in the solenoid valve. It looks like a "U" with a solenoid valve in the bottom of the "U". If it was to close it would do nothing. If it was open it would do nothing. I should mention that between the two T's is about a 2 inch "coupler". The "coupler" looks stock as if it may have a screen or something in it??

The unit is a mess. Looked like a low charge then I found the temp drop. Switched it to heat and looks ok, toggled back to cool and it tried to run into a vacuum. The wiring has been hacked and it has a new compressor that was hacked in. Not even a filter drier in this thing. The refrigerant doesnt stink and the oil tests free of acid or Id be walking away. I plan to recover, blow it out, open both distributor assemblies, check for clogged screens, install filter drier, rewire, and see how it goes.

Sry this got so long. Couple questions id really like help on.
WTH is the solenoid valve for?
Is there any type of 3/8 valve i could install on each side of the filter drier so I could do multiple drier changes without pulling the charge?
Would you guys even mess with this unit? Its a very young couple with a new baby. Hes going to have to get a loan for me to do the repairs.

Thanks in advance.