There isn't a drain plug in the typical sense for the refrigerant in a 1994 Chevy Camaro Z28's air conditioning system. The system is sealed. To remove refrigerant, a technician uses specialized equipment to vacuum the system out. There are access points for the service ports (usually low and high side) where the technician connects the vacuum pump and refrigerant charging equipment. These ports are usually located on the accumulator/dryer.
Do not attempt to drain or service the A/C system yourself. Refrigerant is under high pressure and is harmful if released. Improper handling can cause serious injury and damage to the system. Take your vehicle to a qualified automotive air conditioning technician for any service or repair.
