My AC is empty but I want to make sure everything works. I need to know how it works. Also the pressure switch has 4 wires/ terminals and I can only find two terminal switches online. Will the compressor clutch engage with no pressure in the system? I'm sorry I would post a pic but I haven't figured it out yet.

Just run 12v to the compressor to get it to engage. As far as your ac being empty, but you want to make sure everything works.....don't know how you plan on doing that with an empty system. If it's been empty for a while you might as well replace all the o-rings, expansion valve, the high/low pressure switches, and receiver drier. You can get all those parts for under $100 from Pelican. If you are unfamiliar with working on an ac unit, I would suggest reading up on it first and watch a few youtube videos on how to vacuum down the system, check for leaks, etc., etc.

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1990 190E 3.0L

I ran 12v to the clutch and it's good, but what I'm having trouble with now is this pressure switch. Like I said before I can't find one that looks like it on eBay or any where else. It has 2 term at 12 o'clock and 2 at 3 o'clock. I don't know how I would go about converting it to the other style which I noticed has two sensors each with 2 terminals. I know how to work on AC systems the problem is finding replacement parts that match what I got. This is why I'm asking anyone if they know of different AC setups in there 123s. From what I was told from my father who bought the car new,. Was he had the ac system installed after it was bought. It is a European car but this was installed in the US. (Along with some emmision crap) I'm sure I could change over parts and sensors and make everything work but I'm trying not to create more problems. Any info would be appreciated.