SL-Class (R230) 2003 -- 2012: Discussion on the SL500, SL550, SL600

SL/R230: Interior light auto dimming continuously

Old Feb 20, 2019 | 01:50 PM
  #1  
Breakout16's Avatar
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SL 500 R230 '04
Question Interior light auto dimming continuously

Hi Guys, I have an issue with my interior lights on my 2004 SL500 at the moment. For no reason they will go bright and then dim and continue doing so at various intervals. I'm assuming these do auto dim depending on the outside lighting conditions and so I'm suspecting it may be a faulty sensor. Does anyone know where the sensor is and how to test it please?
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Old Feb 20, 2019 | 08:47 PM
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Welcome to the forum! Please take a moment to visit the User Control Panel and update your profile to include your location (at least country). This information will then appear below your name and avatar on the left side panel next to each post you make. This will greatly help others to give you better information. If you are using the mobile version of the site, you will need to switch to the "full" version to get to the User Control Panel.

Are you talking about the instrument panel backlighting? If so, it is not automatic. It is controlled by twisting the odometer reset stalk in the center of the cluster.
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Old Feb 20, 2019 | 09:15 PM
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From: Gloucestershire, England
SL 500 R230 '04
Originally Posted by Rudeney
Welcome to the forum! Please take a moment to visit the User Control Panel and update your profile to include your location (at least country). This information will then appear below your name and avatar on the left side panel next to each post you make. This will greatly help others to give you better information. If you are using the mobile version of the site, you will need to switch to the "full" version to get to the User Control Panel.

Are you talking about the instrument panel backlighting? If so, it is not automatic. It is controlled by twisting the odometer reset stalk in the center of the cluster.
Hi Rudeney, thanks for the reply and yes apologies I will update my details when I get back to the main site and not my mobile. Yes, I think I'am talking about the instrument backlighting but does this include the clock display, the heating control lighting, the comand display etc. I can see that the Odometer reset stalk does the brightness of the instrument cluster but the other lighting as I've listed above has a mind to change between bright and dim. If these things are not connected does that mean I have a deeper problem?
Thanks again
Tim (UK currently on GMT)
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Old Feb 20, 2019 | 10:27 PM
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They are all controlled by the stalk. If you try turning the stalk back and forth, sometimes this will fix it. If not, then there is a problem with the CAN bus signalling. The stalk is directly tied to the instrument cluster, but to set the brightness of the other cabin components, the cluster sends digital signals over the CAN bus that are received by the other devices.
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Old Feb 21, 2019 | 02:47 AM
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2005 R 230 SL350 (M112 3.7). Sold the 1966 W113 230SL recently
The Comand head unit has an ambient light sensor just above the ‘1’ or ‘2’ button. With the unit set to automatic, the screen will adapt its brightness plus toggle between day and night display.

Last edited by Frederick NL; Feb 21, 2019 at 02:49 AM.
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Old Feb 21, 2019 | 09:57 PM
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The ambient light sensor on the COMAND unit will only switch it between binary "day" and "night". It won't do any analog dimming of the screen. it also would not have anything to do with the backlighting of the other panels (ACC, clock, etc.)
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Old Feb 23, 2019 | 12:06 PM
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Another trivial pursuit - I confirmed today that my NTG1 screen gradually dims as my finger covers the ambient light sensor. My finger couldn’t make it switch to night display in the bright sunlight.
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Old Feb 23, 2019 | 02:52 PM
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Hmm, Frederick, you might be right about that "eye" being used to dim the screen. I re-read the owner's manual for COMAND and the settings for day/night/auto actually use the vehicle's light sensor, so that's why covering it on yours does not switch to night mode.

Regardless, that should not affect the crazy dimming of the backlights the OP is experiences on the other panels. That sensor is just for the COMAND screen.
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Old Feb 23, 2019 | 04:46 PM
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It’s a pity that so many of its tricks are ignored in the R230 manual.
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