We own a SubZero Model 632F. For the past 2 years, we have had to recharge the refrigerant. Most articles refer to a leaking evaporator as the most common cause. Given the age of the unit (17 years), it has been far less expensive to simply add freon. We finally inspected the compressors ourselves, and noted that (unlike current SubZero models) both have easily accessible, built in R134A ports, but they don't seem to match the R134A port for automobile low side A/C units. We would love to find a work-around ie [I]some adaptor that could be placed on the SubZero side that would allow me to use readily available R134 refrigerant. Please advise.