A/C systems can be winterized two ways. Putting antifreeze into the strainer and sucking it into the system with the a/c pump until it comes out the side of the boat or putting the antifreeze in the discharge and forcing it backwards until it comes out the bottom of the boat at the strainer. On Formulas, going through the strainer is the easiest and fastest method. I personally drill and tap the strainer lid and install a 1/2 inch boiler drain cock permanently to allow easy and fast winterization year after year.