Before I sell the vacuum pumps, I test them with a 12 volt source. In my case I use a battery charger.
I apply the negative cable to the brown wire of the pump. Ground.
Applying the positive to one of the other wires will make the pump push air or suck air. Depending on which wire I started with.
The pumps I work with are the ones with the three wire pig tail. The newer ones have a second connection.
I don't get into those yet.

Looking closely at the pig tail you will notice it's shape. There is a flat surface on the round male plug. In order not to plug the pump in incorrectly, the male plug inserts so the flat part contacts it's mate within the female part.

I can not confirm if the pump it always suppose to "suck" air when connected correctly. But if you can match up the color of the wires from the car with the pig tail your task is done.

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Selling used Mercedes parts on Ebay...always changing...
cdplayer51 take a look!
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