The aim adjustment of the headlamp unit on the Mercedes Vito W639 is quite a simple task to perform and is outlined below.  I had noticed whilst driving at night that the nearside headlamp was aimed slightly lower than the offside and required some adjustment to lift it slightly. Before you begin start the van and set the electric headlamp level control to ‘0’ – its highest lift position, shut off the engine, lift the bonnet (hood) and find the the location of the adjustment screws as outlined in the photographs.

You will need to insert and rotate a 6mm long hexagon key to make the adjustment.

Standing at the front of the vehicle the outermost adjustment screws move the beam in or out, or to the left or right van.  Clockwise rotation of outermost adjusters (the ones nearest the wings) will move the beams toward the left of the vehicle in both cases.

Anti-clockwise will move either beam to the right in both lamps.  The innermost lamp adjusters (the ones nearest the bonnet catch or hood release) will raise or lower the beam of either lamp.  Anti-clockwise rotation lifts either lamp beam, clockwise lowers it.

This simple procedure allowed me to make the slight trimming adjustment required but if you need to do a a more thorough  alignment I found this quick-guide to how to obtain correct alignment without a professional beam setter.  Further reference to the UK MOT headlamp conformity read here (Ref. Chapter 1.8 page 3).