ProSeal XL4 is designed for repairing leaks in condensors, evaporators, copper line, and solder joints. This product is an epoxy that reacts to water and air. When coming in contact with the atmosphere, it forms a seal over the leak. If your system stays charged for one day when running, this product will fix most leaks that you may encounter.
If there is air and water in your system, pull a deep vac on the system and boil moisture out of the system. Another option is to purchase ProDry to turn moisture into synthetic oil. This will prevent ProSeal from reacting inside your system.
In most cases, if a system has not leaked all the way to zero, there is typically not air or moisture in the system. The system has greater pressure than what the atmospheric pressure is and cannot leak unless the system is at zero. ProSeal XL4 has twice as much sealing agent as regular ProSeal. It is great for repairing those recurring leaks in systems. Save on costly repairs, use ProSeal XL4 instead.
PROSEAL XL4 (Each) - $19.95