Performed ac diagnostic 21 yr old gas package unit roof. Found that system is appearing low on refrigerant. Or it has a bad metering device. Won’t know until we try adding refrigerant. System is older and has the r22 refrigerant. Refrigerant shouldn’t leak, it’s a sealed system so it had to go somewhere. Will need to charge system with correct amount of refrigerant for system to cool properly. Before I can see if anything else is going on. added dye to system and then charged system with 2 lbs of refrigerant. Numbers improved. See picture. Dialed in refrigerant charge. Signed up on maintenance plan.