Uhh, I don’t think the silver box is your problem. Or at least it isn’t your only problem.

There is nothing special about those caps they are just electrolytic capacitors. You can order regular radial leaded capacitors at Mouser or find cheap ones elsewhere online. The specs are on the side of the cap. Make sure your voltage, capacitance and lead spacing matches. Take photos and make notes of where each one came out.

Your relay on the klima should send either 12v or nothing to your compressor clutch. The fact it’s putting out a few mV tells me there’s a bad connection somewhere between the relay and end of the plug.

Yeah the caps look leaked out in your silver box. I think that means the temperature control won’t work well. The push button unit should still send a command signal to turn the compressor on when it is on max cool. The silver box doesn’t turn your compressor on and off. On these cars the compressor is turned on then the silver box does things like modulate the fan and hot water monovalve to stabilize the temperature. The compressor is always on.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles