I finally know how to aim the headlights

... having taken 3prongpaul's advice last weekend and changed my HV coolant pump preventively (it was still working just fine at 206,000), which is easiest to do by taking a headlight out.

I had never been able to make any sense of the picture in the manual:

where the callout points to some weird thing that didn't look like anything I could see from any angle when I looked at the actual car. I wanted to find it, because for as long as I've had the car I've noticed people occasionally flashing lights at me when my low beams are on, so I think they're a little too high.

With the headlight out, I could finally see the secret. That weird thing is really there, but it's way at the bottom of the headlight, as you'd never guess from the picture, which also doesn't show that you access it through the hole in the sheet metal behind the top of the headlight:

The weird thing is a screw shaft with a wide, toothed head. You stick a long-shanked, probably Phillips, screwdriver down through the hole, and there are even guides molded on the back of the headlight to lead the shaft straight down to the adjuster head. Your screwdriver meshes with the teeth, you twist the driver left or right, and the reflector moves inside the headlight assembly to vertically aim the beam.


Clever ... but I've got to say I've usually found the manual to explain things really well, and this was, ahem, an exception.

-Chap

 

Yeah, they do leave you to infer a lot. The key seems to be that the high beams should go straight ahead, so the horizontal line for the high beam centers should be exactly as high as the headlight centers above the ground (with properly inflated tires, full gas tank, and a driver in the seat). They can't tell you what that height is exactly, because they don't know how worn your springs are, what the driver weighs, brand of tires, etc., so the best bet is probably to fill a clear hose with water, hold one end with the water level right at the center of the lamp in the headlight, and mark the target at the water level of the other hose end. Then you know the low-beam cutoff should be 30 mm below that. (What can they mean by "29.7"? Do they think you'll be able to pin down the edge of a light pattern to 0.3 mm?)

The water-level trick assumes the surface the car is parked on really is level. Otherwise you could measure the slope and correct for that too.

I have no idea why they don't include a number for the horizontal distance W -- it's not like the saggy spring/what does the driver weigh problem for the vertical measurement. They know how far apart they built the headlights! But no, you have to measure that too. If you get a good figure it would be worth posting here. Would need something like a meter stick and two smaller rulers (to measure equal distances from the meter stick back to both headlight lenses, to make sure the stick was truly perpendicular).

Also, their math is weird. arctan(29.7mm/3m) is 0.57°, not 0.4°. 3m times tan 0.4° would be more like 21mm. Not sure which they meant ... but it might not matter if there's only one adjusting screw anyway, depending on whether it changes both beams or just the low. If it changes both, their relationship is probably fixed, and you'll find out whether it's closer to 21 or 30.

As you can tell, even though I figured out the adjuster more than a year ago, I haven't gotten around to fussing with the adjustment yet.

-Chap