On Single DIN units, Orange and Yellow are 12V, one is constant, and one switched...I can't remember off the top of my head which was which (VW had them reversed to 'normal'). It's all detailed in a a thread I created in this forum...search on my name. I mention this as you've said you''ve connected white to orange...it's clear from your posts whether the metra harness colors match the vehicle harness colors or not..

It'd seem strange to me that VW would still have a dimmer line, but not switched power.