Just checked the wiring from the low pressure switch (blue/red): one switch goes to the push button climate control unit to pin 6 (or whatever pin the blue/green wire is) which shows continuity, the other goes to pin 3 of the MAS unit, which also shows continuity. The 3 connectors on the ac compressor (red/blue,white/blue,blue/green) all show continuity to their respective pins on the MAS relay (pins: 22, 5, 6). I swapped out both the MAS relay and the climate control unit to see if there was any change and there was none.

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1990 190E 3.0L