2014 C63 coupe with lighting package.

Pull out of the garage this morning and noticed the headlights never turned off. The dash lighting got brighter as did the entertainment display so whatever sensor controls that appears to be working.

Messed about with the headlight switch a bit whilst hurtling towards work and never got them to turn off as they should in auto mode. In addition, pushing the high beam switch forward just turned on the high beams and didn't put them into auto-standby.

Haven't noticed any error messages on the info screen, no warning lights on etc. Headlight switch going bad or something else?

I searched a bit and didn't find anything related.

 

turn off your rear fog light? Its designed to turn on your full light package it seems and won't allow high beams

 

Pushed that thing on and off too this morning without any change. To be clear, the high beams come on just fine manually, it's the auto on/off function that's hosed along with the regular headlights as well.

 

check your setting in the menus then, might have been changed

 

Was someone else driving your car?

 

Never. It's been sitting in the garage since last week when I drove it and it worked fine then.

 

Those headlight switch modules go bad a lot it seems, might be that https://mbworld.org/how-tos/a/merced...-switch-388504

But based on your description of auto high beam not working and the headlights not turning off I think it could be related to the sensors on the windshield that pickup on coming headlights and if it is day or night. I suspect the dash lights may have their own sensor for ambient light inside the car.

 

Thanks for the link to the article.

The sensor thing is interesting. Makes sense that the ambient light sensor is different. The auto-lights sensor(s), are they run off that camera above the rear view? Maybe I've got something blocking it? I'll have a look when I get off work.

 

Just a shot in the dark but guessing if it won't autoswitch highbeams then that could be the camera/sensor thing on the windshield and that same sensor could sense ambient light possibly, not sure what it uses for ambient light, but still could just be the switch and those things are not functioning because of the switch. Just not sure how you troubleshoot without another switch or xentry to diagnose. The switch does fail fairly often the sensor I have not read of any failures that I recall.

But ya check the sensor in case a bug crawled in there and is blocking it or something.

 

Don't see anything blocking the sensors on the windshield. Guess I'll bring it to the dealer to have a look before I start throwing parts at the thing.

 

By any chance was the windshield replaced lately? Was the camera re-calibrated to the new windshield or does that matter for our cars? Is that where the auto high beam sensor is?

 

The Stealer will most likely throw parts at it.

 

Good question but no, it's all original.

 

There are two issues, no doubt related.

1) The auto headlights don't turn off when it's light out, they're just on always
2) the auto hi-beams don't work any longer. Flipping the stalk to hi-beam in auto mode should make it so that they come on and off as needed. It doesn't, the hi-beams just turn on and stay on.

Since the ambient light sensor works fine for the dash lighting, either it's a different sensor for the auto headlights (I doubt it) or something else is broken, The auto hi-beam sensor is one of the bits above the rearview mirror on the windshield facing forward.

Since both of these functions aren't working, I'm guessing that two separate sensors didn't fail at once but rather a common piece is broken. That common piece could be the light switch or it could something else altogether.

 

Probably but I have a warranty. They'll do so without dipping into my pocket beyond the deductible. However, I might try the $50 switch on my own and see if that helps as that's the same as the deductible.

 

So to close the loop on this in case anyone has the same problem down the road and searches for a solution, the replacement headlight switch fixed the issue.