I bought a used central-door-lock vacuum pump for 1988 300E W124. To quickly test it, I applied 12V Battery supply to its power terminal with proper polarity. But nothing happened. There are also a three-wire plug for, I think, control signals; perhaps I need to connect these wires as well. Please let me know, thanks.
How to test a central-door-lock vacuum pump for 1988 300E W124 body? on 1990 Mercedes-Benz 300E