What's the brand and model number of the harness you got? Perhaps it's the wrong one? The one I used was a Schosche VW01B


Note that the chart above shows the colors and the illustration shows the back of the factory head unit. So the positions of the pins on the car plug are mirrored when compared to the appearance of the harness plug attached to the head unit, which should match the drawing.

This is what the car plug looks like:



You should not be getting the pop when it comes on.