Came out to call for a system not cooling properly. Customer stated that it just seems to run non stop, so they shut it off for now. I cycled the system on from the thermostat and checked the AC over. Found it to be very dirty and also low on refrigerant. I washed the condenser coil thoroughly, then let the system dry out and rechecked charge. Let customer know that the system is low on refrigerant. Due to the age, condition, and refrigerant the system uses, I recommended replacement of the system. Customer stated they are planning on replacement, but need to get it going for now. I added 4.2lbs of R-22 to get correct superheat on system. I was actually able to locate the systems leak as well. It is in the liquid line king valve and is leaking through the cap. Told customer I could put pipe sealant on it, to slow down the leak, but I can’t guarantee how long the refrigerant will last. Customer is aware of the leak and visually saw it leaking. Customer paid $500 in cash and will come