Mercedes-Benz Automatic High Beam On

To turn on the auto high beam on a Mercedes-Benz, push the turn signal switch forward, and it will stay there, turning on the auto high beam feature.  Pull the turn signal switch towards you to turn off the auto high beam feature, and the auto high beam function will be canceled.

Auto high-beam system can automatically turn on the high beams when its windshield-mounted sensors detect no vehicles ahead. The auto high-beam system switches to the low beams when vehicles are detected early.

To turn on the auto high beam feature on a Mercedes-Benz, follow these steps:

1. Set the headlight switch to AUTO. 
2. Push the turn signal switch forward. 
3. Ensure the AUTO or high beam with the A symbol stays on. 

The auto headlight feature is most helpful when driving on secondary or country roads when no other cars are on the road. They can also be used on the highway if there is insignificant traffic. The high beams may stay off if the highway has street lights. This does not mean your Mercedes-Benz auto high beam system is not working.

You can use this function to automatically set the headlamps between low and high beams. The system recognizes vehicles with their lights on, either approaching from the opposite direction or traveling in front of your car. It consequently switches the headlamps from a high beam to a low beam.

The system automatically adapts the low-beam headlamp range depending on the distance to the other vehicle. Once the system no longer detects cars in front of you (moving in either direction), it reactivates the high-beam headlamps.

The system’s optical sensor is located behind the windshield near the overhead control panel or at the top of the windshield. Adaptive Highbeam Assist may fail to recognize other road users with lights or may recognize them too late in sporadic cases. If the system fails to dip for other road users, switch it off and control the high beams yourself, dipping them for oncoming traffic and for vehicles ahead of you.

Why it may not switch on even when enabled

Most reports of this feature not working turn out to be the system behaving exactly as designed, because it only operates inside a fairly narrow set of conditions. Before assuming a fault, check all of the following.

The light switch has to be in the automatic position. Turning the headlights on manually takes the system out of the loop entirely, and this is by far the most common reason it appears dead.

There is a minimum speed. The system will not switch to high beam until the car is moving at roughly 25 to 30 miles per hour, and it drops back to low beam as you slow below that. Testing it in a driveway or a parking lot will never work.

It needs genuine darkness. In an area with street lighting the camera sees enough ambient light to conclude that high beam is not needed, so it stays on low beam. It also stands down in fog, heavy rain and falling snow, because high beam in those conditions reflects back and blinds the driver rather than helping.

Finally, it will not raise the beam while it can see another vehicle, including the tail lights of a car some distance ahead. That is the entire point of the system, but it does mean that on a moderately busy road it may spend the whole journey on low beam and look as though it has failed.

When it genuinely is a fault

If the conditions above are all satisfied and the function still does nothing, start with the windshield. The camera looks out through a small area of glass in front of the mirror, and anything in that patch stops it working: road film and interior haze on the inside of the glass, ice, a chip or crack in that exact spot, or a sticker, toll transponder or dash camera mounted in its field of view. Clean both sides of the glass there before anything else.

A failed bulb or LED module in either headlight will also disable the function, because the system will not operate a lighting setup it cannot fully control. Walk around the car at night and check every lamp.

If the windshield has been replaced at any point, that is a strong candidate. The camera is calibrated to the exact position of the glass it looks through, and replacing the windshield moves it. The calibration has to be redone afterwards with the manufacturer’s procedure, and budget glass sometimes has enough optical distortion in the camera area to prevent calibration completing at all. If the feature stopped working within days of a glass replacement, go back to the fitter before paying anyone to diagnose it.

Where none of that applies, the fault is stored as a code in the camera or lighting module rather than in the engine module, which is why a basic code reader shows nothing. A full system scanner that accesses Mercedes body and assistance modules will read it and say whether the camera, the lighting control or a supporting input is at fault.

Frequently Asked Questions

How do I turn on automatic high beams on a Mercedes-Benz?

Set the headlight switch to AUTO, then push the turn signal stalk forward. A high beam symbol with an A appears in the cluster when the system is active.

Why does my Mercedes stay on low beam with the assist turned on?

The system only switches to high beam in the dark, above a certain speed, with no vehicle lights ahead. On busy or lit roads it stays on low beam.

Why is automatic high beam not working?

A dirty windshield in front of the camera near the mirror is the most common cause. Clean the glass inside and out.

Does the camera need calibration after a windshield replacement?

Yes. The camera must be recalibrated after the windshield is replaced or the system may not work correctly.

More guides: browse all of our Mercedes-Benz repair and troubleshooting guides.

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