Hello! I have a 05 MCS cabrio R52. In the last week or so I noticed that the Xenon headlights are suddenly aimed high. People are flashing me, and the cutoff is def way higher than it should be. They were adjusted perfectly before this, and it's both lights, so I assume it's something with the leveling system. Is there a common problem to cause this, or a good way to troubleshoot? Have you run into this before?

Thanks! Jeremy

 

The headlight leveling system uses sensors on the left front and left rear suspension that measure how high the suspension is sitting. One of the sensors might have come loose or gone bad.

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Thanks, I think the front sensor is flaky, or the circuit is. I jacked up the left side, disconnected both sensor linkages, and turned on the headlights. The lights adjust up and down in response to rear sensor arm movement, but are flaky with front sensor. Sometimes they move, sometimes not.

I hate throwing parts at problems though. Is there a way to test these? My Bentley manual is extremely thorough in some areas, and woefully lacking in others. It says the level sensors are Hall effect sensors, but really gives no troubleshooting or testing procedure on them. It doesn't really even tell how to change them out, although it's pretty obvious. I have continuity between the 3 pins that are used - two pair show between 400 and 500 ohms, and the other pair shows 60-70 ohms. Since it's a Hall effect sensor, I'm not really sure if the resistance should change when the arm moves. Does anybody know?

I guess I could remove the rear and measure its resistance to see how they are supposed to act.

Do these lil guys go bad very often?

Thanks, Jeremy

 

UPDATE:
The hall effect sensor is not measurable with a common meter while disconnected. I did find a way online to test it while on the car by back-probing the connector, haven't tried that. It was for a Bimmer, but the sensor looked the same.

I found a supposedly good used front sensor on EBay and, while I dislike throwing parts at problems, I figured 20 bucks was OK. I'm pretty sure it behaves the same, will drive it a bit and test more thoroughly.

[size=3]Here's what it does: I went to the rear and moved the sensor arm up and down, and the lights responded quickly and appropriately. I did this for maybe 30 sec, all good. I left it in kind of the middle of the range and then[/size][size=3] went to the front arm to move it. At first it seemed to respond appropriately as well. Then it started "cutting out" if you will...the movement of the lights got inconsistent and jerky, then stopped being responsive altogether. Once the front has done this, the system does not respond to the rear sensor either. Make sense? I see no correlation to wiggling the front harness, or the rear. If I wait, or maybe cycle the car power, it will sometimes work again for a short time. Has anybody run across this?[/size]

I expect, based on this behavior, that it will get stuck at full-high again, should be apparent pretty quickly.

Have any of you disconnected the system entirely and just set them to one height? I experimented a little and it seems like when either sensor is disconnected the system moves the lights to a mid-height, almost exactly in between full-high and full-low. If that is truly the case, and remains consistent, the lights can just be aimed for nominal like any other car. (Yeah, I know about the Xenon thing and the regulation.)

Anybody have experience with this? Thanks! Jeremy

 

Spray contact cleaner on the plug and socket, as resistance will cause the sporatic movements. Make sure all connections are aligned to mate with their counter points!

 

Thanks for the response. I have done that. The connections are clean, pins straight.

 

Wait, Wayne, do you mean the connectors on the leveling sensors, or some other connectors?

 

Still looking for input as to how I can get the leveling system functioning.

At this point the sensor connections are clean as a whistle, and I replaced the front sensor with a supposedly good used one and the problem didn't change. So either the replacement is bad in the exact same way, or there is a problem with the system, wiring, processing unit under the dash, etc. I haven't yet tried to test it by back - probing while connected, should try that. But I'm almost positive by the behavior that the front sensor input is not reliably getting to the system.

So for now I left it disconnected, which appears to make the lights assume a consistent middle position. I am adjusting the level to be appropriate for this.

The high beams... Is there any way to adjust them independent of the low beams?

 

FOLLOW UP:

The system is still not leveling of course because I left the front sensor disconnected. But I have verified thru use that in that condition it consistently goes to some mid-level adjustment with the stepper motors. I set the headlights to a good level and it's working fine, old school, no auto leveling required.