Self levelling zenon headlight fault
 

After getting warning light and message about headlights require service I have been trying to sort out the problem which is on the near side headlight. When switching on ignition headlamp beam does not go up and down like the offside one. Have swapped the control units to no effect. When I connect the offside headlight unit to the near side it does work ok, so the problem seems to be within the headlight unit. The wishbone on the bulb unit seems to move freely. I read somewhere about connecting a p3 battery to the servo to test it. Has anyone tried this and also is it possible to get a replacement servo.
Any ideas gratefully received as a replacement headlamp unit, even secondhand is stupid money. It’s a v70 p3 2011 with xenon ABL