Just a question on the headlights. Is it necessary to turn the headlights on in order to adjust the L-R screw . Also how does the adjustment feature work. How sensitive is the adjustment . What affect is a 1/2 turn or more.

 

It would definitely help to have the headlights turned on while making adjustments, that way you can see what's happening to the beam as you turn the screws.

Do it at night or in a darkened garage. At night on a flat deserted road is best in my experience.

There are two adjustment screws per headlight, one for up/down, one for left/right. They are white coloured allen-head plastic screws, 6mm from memory?

I haven't had to fix one for left/right, but the up/down is quite sensitive, a half turn is a big difference to the aim.

 

If you don't turn on the lights, how do you know what happens when you turn the adjustment screw?

My Post #2 from your old 2--2-2014 thread https://www.jaguarforums.com/forum/x...tments-128452/ :
"Assuming your car is garaged and the floor is level (and you park nose in), when it's dark enough back out a few feet and mark the garage wall with masking tape where the centers of the R and L low beams hit the wall. Also mark the floor so you can position the car in the same place if you need to make adjustments again. With the wall marks as your guide, make the headlight adjustments and mark the final positions on the wall. Test drive and if not to your liking adjust again until you're satisfied."

For details on how to adjust your headlights, read this thread:
https://www.jaguarforums.com/forum/x...ustment-12354/

 

I did mine on the road. Adjusted them up until they would barely reflect on a stop sign 100 yards away. Width was so they were even across my lane. This has worked well for deer and dummies on the side of the road. Factory they are set too low and away from oncoming traffic. The plastic adjusters have little covers that need popped out with a pen knife to access the Allens. I thought it was 5mm when I did mine.

Per how they work, the lamp assy is held to the housing with three ball and socket fasteners. The top and outside one have jack screws attached. Turn the top one the beam moves vertically. Turn the outboard one, it move horizontally. The lamp assy has its own servo movement for the headlamp aiming and there's a shutter for high beam.

 

In Sweden the yearly MOT checks the light and usually adjust it if wrong. If you adjust the light to your liking yourself chances are you dazzle oncoming traffic.

 

They check them here, too.