Originally Posted by ericzacha

1988 300 SEL
It was converted to R134a before I came along. A/C has been gradually getting warmer over the past two years and I figure it's time for a recharge. Did a lot of reading here and other sites about AC systems but still have a couple of questions.
1. If I am just recharging is that considered an "open system", in which case everyone seems to recommend replacing the drier. Mercedes I believe recommends replacing the drier when the system is open and the drier is more than 5 years old. Conversion on this car was done in '99 so I assume it has not been replaced since then. In sum, if I recharge only, should I replace the drier?

2. If I do replace the drier, is that something I can do without vacuuming out the system? As a corollary question, do you need to vacuum out the system every time you recharge

My plan was to replace the drier, since it is 9 years old, and to then recharge with R134a. I just don't want to blow myself up or kill baby seals or whatever badness happens when this stuff gets released. Thanks.