I purchased a 98 ML320 about 2 months ago and I don't think I really tested out the A/C until this week. At first it didn't get that cold and I thought the system was shot, but then, after some use, it got cold, but not as cold as I would have expected. I assume that, because it gets cold, the compressor is OK, and that it may just need a charge. Of course, I have no idea of what it may need. Can MB units just be charged up, or am I looking at a nightmare here? Thanks for your help.