The AC system is supposed to be completely sealed, so as long as there is no r143a lost to the atmosphere the system does not need to be "maintained". It is good to run the AC once in a while in the winter, but leaving the AC switched on and having electronic climate control means that the compressor moves every time the engine is started as part of the ECC check out procedure.

The best thing to do is to change the cabin filter annually and keep the engine cowl area free from leaves and other dirt. Depending on the year, 1993-2000 specifically, it is a good practice to turn off a running AC about 1 mile from home to allow the evaporator to dry off before engine shut down.
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My name is Klaus and I am a V ♂ lv ♂ holic.