Headlight adjusters

Hi all,

My headlight adjusters sometimes "stick" in their highest setting, with the motor making unhappy noises and the beam vibrating up and down slightly. The right hand headlight does it a lot, the left hand occasionally. The dealer's tried new motors, and an entire headlight from another car - neither made any difference - so I don't think it's the motor that's faulty.

I'm wondering if the adjuster is telling the light to go too high, and then it's getting stuck there.

Is there anyone out there with working adjusters who could unplug the wires from the back of one of their headlights and tell me the voltage on the brown & white wire (with the ignition & dipped lights on, but the engine off) when the adjuster's in its min & its max settings. Mine is reading 4.6V to 10V for lowest to highest.

If that isn't the problem, I haven't got any idea what's wrong with it...

Thanks,

Alan