Understanding the operation of the light sensor

mcat · 10-30-2007

I would like to get a better understanding of the light sensor's operation in relation to the headlamps, dimming mirrors, comand display and autowipers.

The following used to happen before Mercedes Benz fiddled with the settings

- At dusk the dimming mirrors start to take on a green hue (slightly dimmed)
- Lights appeared to come on when they should
-comand display switches readily between night and day at levels I was happy with
- Autowipers were sometimes a bit slow of the mark.

And then when MB were upgrading my comand system they said they also reset the sensitivity of the light sensor as it was mismatched for the type of glass!!

I have not driven much since then to fully see the implications but the following now seem to happen.

- mirrors stay clear at dusk (good)
- lights come on more readily (not bothered)
- comand switches to night mode unless there is bright sunshine!!
- not driven in the rain so no idea what the effect on the auto wipers is.

I mention this to the tech when I dropped my car off for some body work. He said the comand should switch to night mode whenever the lights switch on. I am not sure I agree with that. Before they fiddled the two seemed to work independently of each other. My lights could be on and the comand will still be in day time mode.

So what is the true story. At what ambient light level should all these things switch?

DansSlk · 10-30-2007

They've not properly coded the RLS and now its malfunctioning.

It should work as follows -

Lights on at dusk
Interior lighting on shortly after lights
COMAND to night mode with interior lighting

The auto-dim mirrors are an independent system the rear view mirror has its own integrated sensor so it was likely a glitch that was causing them to dim when it got dusk, they should only dim when they see more light on the inside of the car than they do on the outside but i have seen some that do dim partly in dusk and we could find no reason as to why.

Sometimes the rain part of the sensor is a little slow off of the line to be honest with you.

The exterior and interior are 2 totally different systems to long as you have a light sensor installed, the exterior lights will come on first normally followed by the interior even if you where to set the exterior lights to off the COMAND would still switch and the interior lights would still come on.

The light switch has no effect whatsoever on the interior.

mcat · 10-30-2007

Quote:

Originally Posted by DansSlk

They've not properly coded the RLS and now its malfunctioning.

It should work as follows -

Lights on at dusk
Interior lighting on shortly after lights
COMAND to night mode with interior lighting

The auto-dim mirrors are an independent system the rear view mirror has its own integrated sensor so it was likely a glitch that was causing them to dim when it got dusk, they should only dim when they see more light on the inside of the car than they do on the outside but i have seen some that do dim partly in dusk and we could find no reason as to why.

Sometimes the rain part of the sensor is a little slow off of the line to be honest with you.

The exterior and interior are 2 totally different systems to long as you have a light sensor installed, the exterior lights will come on first normally followed by the interior even if you where to set the exterior lights to off the COMAND would still switch and the interior lights would still come on.

The light switch has no effect whatsoever on the interior.

What do you mean by the interior lighting? Is this the courtesy light that goes on when I open the door. I never thought about it before but are you telling me the door light only comes at night?

What is the RLS stand for?

cheers

DansSlk · 10-30-2007

Interior lighting - All the lights on the inside of the car and on the doors, so thats the overhead lights, the puddle (courtesy) lights on the doors, the footwell lighting and the LED's for the console buttons.

They are not switched on during the day only at night, it saves the bulbs.

RLS = Rain and Light Sensor

mcat · 11-01-2007

I had the dealer check out my car today. I watched them on the Star Diagnostics. When they looked at the setting for the RLS it was blank. They tried to pick a setting (it is not clear which to pick either as there is about 5 options for r171 with no indication which to use) but no matter what he selected the RLS just would not store the setting and it kept returning to blank. The conclusion is that the whole mirror/light assembly unit is bust so they have ordered a new part which will come in next week.

In the mean time:

- My Comand is stuck on night mode
- My dimming mirrors won't dim
- My auto wipers think there is always water on my car
- My auto head lamps are permanently on

As Dan said I am not sure these all go through the same system so why would they all be inoperable at the same time. I don't hold out much hope of the new part solving the problem.

DansSlk · 11-01-2007

I have had a look into this again mate and numbers 1, 3 and 4 are all managed by the RLS.

Number 2 is its own system but it does pass via the OCP so if it has failed then that could explain all 4.

But that would be a weird one if the buttons on it still work OK and all the interior lights come on when you open the door.

I am sure you already know mate but just in case -

COMAND can be set to day mode in settings
Wipers can be killed with stalk
Lights can be shut off by setting the light switch to O and setting headlamp mode to manual in the cluster.

As for the settings they depend on the type of glass and the installed lenses, perhaps this 'tech' should sit down and read the WIS before he starts playing with expensive bits of kit.

mcat · 11-02-2007

Quote:

Originally Posted by DansSlk

But that would be a weird one if the buttons on it still work OK and all the interior lights come on when you open the door.

As for the settings they depend on the type of glass and the installed lenses, perhaps this 'tech' should sit down and read the WIS before he starts playing with expensive bits of kit.

This would make sense as well. As the car thinks it is always night then the interior lights will always come on when the door is opened - which they do.

As for the type of glass and lens - why would they be different from r171 to r171. Don't we all use the same glass?

DansSlk · 11-02-2007

Its weird normally if the OCP breaks the lights stop working.

As for the sensor settings, the SLK has more than one type of glass available and different lenses depending on the chassis number and the particular sensor version.

Perhaps they should have stuck to the old if it ain't broke don't fix it rule

mcat · 11-19-2007

Well, before the car was to go back in to have the whole sensor assembly replaced it started working again. I still went back to the dealer to get it checked out to make sure but told them not to replace anything. Everything was fine.

When there I asked them to upgrade the head unit so that I can get the ETA function on the front screen. They did it and I signed something so not sure if I will get a bill later or they did it as part of warrenty work.

**etyu** · 11-19-2007

Quote:

Originally Posted by mcat

Well, before the car was to go back in to have the whole sensor assembly replaced it started working again. I still went back to the dealer to get it checked out to make sure but told them not to replace anything. Everything was fine.

When there I asked them to upgrade the head unit so that I can get the ETA function on the front screen. They did it and I signed something so not sure if I will get a bill later or they did it as part of warrenty work.

Glad it got sorted out by itself.

DansSlk · 11-19-2007

Warranty covers that normally

10-30-2007	#1 (permalink)
mcat Founding Member #3 Join Date: Jun 2006 Location: Switzerland & UK Vehicle: 2006 SLK350 MT LHD & 2009 SLK350 7G RHD Posts: 274 Country: Thanks: 1 Thanked 4 Times in 4 Posts	Understanding the operation of the light sensor I would like to get a better understanding of the light sensor's operation in relation to the headlamps, dimming mirrors, comand display and autowipers. The following used to happen before Mercedes Benz fiddled with the settings - At dusk the dimming mirrors start to take on a green hue (slightly dimmed) - Lights appeared to come on when they should -comand display switches readily between night and day at levels I was happy with - Autowipers were sometimes a bit slow of the mark. And then when MB were upgrading my comand system they said they also reset the sensitivity of the light sensor as it was mismatched for the type of glass!! I have not driven much since then to fully see the implications but the following now seem to happen. - mirrors stay clear at dusk (good) - lights come on more readily (not bothered) - comand switches to night mode unless there is bright sunshine!! - not driven in the rain so no idea what the effect on the auto wipers is. I mention this to the tech when I dropped my car off for some body work. He said the comand should switch to night mode whenever the lights switch on. I am not sure I agree with that. Before they fiddled the two seemed to work independently of each other. My lights could be on and the comand will still be in day time mode. So what is the true story. At what ambient light level should all these things switch?

10-30-2007	#2 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,756 Country: Thanks: 96 Thanked 221 Times in 173 Posts	They've not properly coded the RLS and now its malfunctioning. It should work as follows - Lights on at dusk Interior lighting on shortly after lights COMAND to night mode with interior lighting The auto-dim mirrors are an independent system the rear view mirror has its own integrated sensor so it was likely a glitch that was causing them to dim when it got dusk, they should only dim when they see more light on the inside of the car than they do on the outside but i have seen some that do dim partly in dusk and we could find no reason as to why. Sometimes the rain part of the sensor is a little slow off of the line to be honest with you. The exterior and interior are 2 totally different systems to long as you have a light sensor installed, the exterior lights will come on first normally followed by the interior even if you where to set the exterior lights to off the COMAND would still switch and the interior lights would still come on. The light switch has no effect whatsoever on the interior. __________________ One thing you will learn with German cars - If it's simple it ain't happening.

10-30-2007	#4 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,756 Country: Thanks: 96 Thanked 221 Times in 173 Posts	Interior lighting - All the lights on the inside of the car and on the doors, so thats the overhead lights, the puddle (courtesy) lights on the doors, the footwell lighting and the LED's for the console buttons. They are not switched on during the day only at night, it saves the bulbs. RLS = Rain and Light Sensor __________________ One thing you will learn with German cars - If it's simple it ain't happening.

11-01-2007	#6 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,756 Country: Thanks: 96 Thanked 221 Times in 173 Posts	I have had a look into this again mate and numbers 1, 3 and 4 are all managed by the RLS. Number 2 is its own system but it does pass via the OCP so if it has failed then that could explain all 4. But that would be a weird one if the buttons on it still work OK and all the interior lights come on when you open the door. I am sure you already know mate but just in case - COMAND can be set to day mode in settings Wipers can be killed with stalk Lights can be shut off by setting the light switch to O and setting headlamp mode to manual in the cluster. As for the settings they depend on the type of glass and the installed lenses, perhaps this 'tech' should sit down and read the WIS before he starts playing with expensive bits of kit. __________________ One thing you will learn with German cars - If it's simple it ain't happening.

11-02-2007	#8 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,756 Country: Thanks: 96 Thanked 221 Times in 173 Posts	Its weird normally if the OCP breaks the lights stop working. As for the sensor settings, the SLK has more than one type of glass available and different lenses depending on the chassis number and the particular sensor version. Perhaps they should have stuck to the old if it ain't broke don't fix it rule __________________ One thing you will learn with German cars - If it's simple it ain't happening.

11-01-2007	#5 (permalink)
mcat Founding Member #3 Join Date: Jun 2006 Location: Switzerland & UK Vehicle: 2006 SLK350 MT LHD & 2009 SLK350 7G RHD Posts: 274 Country: Thanks: 1 Thanked 4 Times in 4 Posts	I had the dealer check out my car today. I watched them on the Star Diagnostics. When they looked at the setting for the RLS it was blank. They tried to pick a setting (it is not clear which to pick either as there is about 5 options for r171 with no indication which to use) but no matter what he selected the RLS just would not store the setting and it kept returning to blank. The conclusion is that the whole mirror/light assembly unit is bust so they have ordered a new part which will come in next week. In the mean time: - My Comand is stuck on night mode - My dimming mirrors won't dim - My auto wipers think there is always water on my car - My auto head lamps are permanently on As Dan said I am not sure these all go through the same system so why would they all be inoperable at the same time. I don't hold out much hope of the new part solving the problem.

11-19-2007	#9 (permalink)
mcat Founding Member #3 Join Date: Jun 2006 Location: Switzerland & UK Vehicle: 2006 SLK350 MT LHD & 2009 SLK350 7G RHD Posts: 274 Country: Thanks: 1 Thanked 4 Times in 4 Posts	Well, before the car was to go back in to have the whole sensor assembly replaced it started working again. I still went back to the dealer to get it checked out to make sure but told them not to replace anything. Everything was fine. When there I asked them to upgrade the head unit so that I can get the ETA function on the front screen. They did it and I signed something so not sure if I will get a bill later or they did it as part of warrenty work.

11-19-2007	#11 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,756 Country: Thanks: 96 Thanked 221 Times in 173 Posts	Warranty covers that normally __________________ One thing you will learn with German cars - If it's simple it ain't happening.

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