Bouncing headlights

[Chrisv60]

Hi all,
I have the xenon headlamps with cornering and active bending.

Recently, the auto levelling seems to be constantly moving the lights up and down. If I brake even gently, they point to the floor, travelling on the motorway at a constant 70mph they are constantly wavering up and down. I've turned off the active bits in the menu but it's had no effect and there are no fault messages.

Is this normal and I've just not noticed it before? I'm sure it used to just move up and down once when the lights came on and that was it.

I've only noticed it since my recent engine change, could that have something do do with it? Or am I looking for a fault that doesn't exist?

Thanks.

[bomberfr0g]

I also have these, they are controlled by a sensor in the rear suspension(same one controls four c suspension if you have it), and are self levelling to make sure you don't blind folks coming the other way. can seem a bit extreme sometimes if the road is v bumpy or you accelerate hard but this is normal.
The active bending is side to side and is not the same thing, you cannot turn the self levelling off. I love mine since changing out to new bulbs as the old ones were 6 years old, such a difference.
When you start the car it goes through a check process where the lights drop then level up.

[Tannaton]

I didn’t think the self levelling worked when you were driving, I thought it only set the headlamp level when stationary? There is no way the levelling motors in the headlamps could keep up on a bumpy road?

[Chrisv60]

Originally Posted by Tannaton

There is no way the levelling motors in the headlamps could keep up on a bumpy road?

That's what mine seem to be trying to do and it's producing a distracting almost flickering effect. Which is why I'm surprised I haven't noticed it before.

It says online if there's a fault then they should default to the down position and flag a warning message as it's a safety issue.

I guess I'd better get it booked in for a check as it just doesn't seem right.

[bomberfr0g]

The system is a dynamic levelling and does indeed move with every bump.

"The control unit calculates the nominal data on the basis of the sensor data, taking the driving conditions into account. In contrast to semi-static headlamp leveling systems, the actuator motors are then triggered within fractions of a second. To make these quick response times possible, stepper motors are mainly used as actuators on the headlamps."

I recently had a faulty sensor and yes the headlights drop to the lowest position and stop moving, I also got a headlight failure warning message on the dim along with an active suspension failure warning which meant the four c damping did not work leading to a very bouncy ride. New sensor fixed it all and now lights behave properly as does the suspension thankfully.

[SwissXC90]

Originally Posted by Tannaton

I didn’t think the self levelling worked when you were driving, I thought it only set the headlamp level when stationary? There is no way the levelling motors in the headlamps could keep up on a bumpy road?

They do work when driving, but they have a certain hysterisis and delay. So they don't react to sudden road changes (which are generally up and down) but more to vehicle body tile (front/rear)

I've seen mine go up and down slightly on steep hills where the car dove a bit in the nose on braking when going downhill.
At night

[SwissXC90]

Originally Posted by Chrisv60

That's what mine seem to be trying to do and it's producing a distracting almost flickering effect. Which is why I'm surprised I haven't noticed it before.

It says online if there's a fault then they should default to the down position and flag a warning message as it's a safety issue.

I guess I'd better get it booked in for a check as it just doesn't seem right.

Yes, the headlights will go to the lowest point when the system detects a fault.
But this is so extreme that you will REALLY notice it.

If you have any juddering / bouncing of headlamps, then check, firstly, all four tyre pressures. A under inflated tyre will bounce more...

Then if anything is failling it is highly likely the level sensor as this sits under the car on the rear suspension and is exposed to road grime.