So what's this crappy hidden box do then?
 

I must have taken the front wheel off dozens of times but never noticed this wee black box. At some time in the distant past it must have been held to the bracket with two holes and has a weird jointed arm. Please put me out of my misery and educate me what it does - or used to do.


https://the75andztclub.co.uk/forum/a...1&d=1574354037

Do you have Xenon headlights ?

It's the front suspension sensor for the OEM xenon headlamp system. There's a similar one on the rear suspension.

If it doesn't work, the automated levelling system for the xenon dipped beams won't operate. Do you think they operate OK or do oncoming drivers ever flash you?

TC

It's an MOT fail if it's not functional. Some testing stations notice, others don't appear to bother but you'll know about it if it is U/S, as others have mentioned here, you might now understand why you've been flashed by oncoming traffic at night. The clip (in the lower part of the pic.) fastening it to the lower suspension arm often isn't present due to corrosion or the little plastic arm gets bent/inverted or the two ball joints seize (cheap new BMW replacement part readily available/easily replaced). The actual black sensor box detatching from the body fastening bracket isn't so common so you'll maybe need a used assembly

I suppose that it depends on where it is jammed as to whether the headlights are misaligned up and blinding oncoming drivers as suggested as possible by earlier posts on here.

I sussed out on mine that the arm had become disconnected after complaining that my lights were incredibly dim and not lighting up much of the road ahead and someone pointed out that if the self levelling mechanism was faulty or the arm had come off ( which it had ) that the lights might be stuck in the default position pointing downish just ahead of the car and thus hugely diminishing the headlight range.

After checking out the thread and pictures about the correct arm position on this site I managed to reattach the arm at the correct angle and the lights were restored to their correct brightness as they lifted up to the correct position.


Its obvious if they're working properly as you can see the reflection of the lights slowly rise up from rest after the light switch is turned onto main lights ( if there is something in front of you to reflect the lights of course )

Your Post#1 mentioned the 'box' (it's the position sensor sender) was not fixed to the body mounting bracket - "...two holes". I can't quite tell from the image but in all other respects everything appears to be as it should - correct arm orientation, arm 'unbent' and clip to lower suspension arm intact. If both arm ball joints are free to work (I'd remove the plastic arm - a 5 minute job once you have clear access - and clean/grease it just to be sure) then the only problem is to re-fix the 'box' to the body bracket (I'm guessing - by a couple of M3/4 x 35 screws) otherwise the whole assembly will just waggle about.
I've noticed

As you can see it is sort of held by a cable clip which I've replaced by wrapping a choice length of top quality green garden wire - no expense spared here. The arm is covered with dear old Copaslip.

Thanks.

At least it's still in the working position. These gizmos often flip over so the elbowed lever drops onto the suspension arm. In that position they won't work. Basically like this:


https://www.mediafire.com/convkey/32...zm1wi17x6g.jpg

TC