Complete 1 System Goodman Gas Pak Straight A/C: HO stated system was not cooling. Found condenser coil way too dirty. Cleaned it with coil cleaner. Checked charge. Found it low in ref. HO authorized me to add ref. Added 1 lbs of R22. Checked delta t. System was running great. Loss charge due to discharge core valve got stuck. Had to replace discharge core valve. Recharge unit at no charge per Jimmy. Added 2 1/2 lbs of R22. Checked pressures. System is running great at this time.