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Discussion Starter #1
M Class Autolights not working
Hello all,Please can someone help me. I have a 2003 ML Cdi 270,the bother I have is the auto headlights don't work. I have replaced the light sensor on the top of the dash but still no luck. I have looked at the fuse boxes and can't find a fuse or relay that's for this. They work sometimes but not very often,I have noticed that when they do work when I unlock the car the headlights come on for about 5secs. When they work they will always work if I leave the switch on Auto but if I switch to sidelights or headlights they will not work again. I would really appreciate any help on this,I think it is a comman fault on this model ?
 

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2004 CLK 240 Coupe
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11,377 Posts
The sun sensor (B32) on the dash is NOT for the auto lights. It is part of the automatic a/c system and 'modifies' the interior temperature accordingly on sunny days.

The sensor that affects the auto lights is the combined rain/sun sensor (B38/2) that is located at the top of the windshield. This sensor also triggers the auto wipe function, if set.

Have you had your front windshield replaced ever? If so the installer may have made a bad job of installing the sensor to the glass. Glue may be affecting the light path....
 

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Discussion Starter #3
I see ,well that explanes why that did not fix the Auto lights:D. It does not have auto wipers just the headlights. I have also never had the windscreen replaced. They do work sometimes,I found on here someone had the same bother but never found the cure to this. I will try and disconnect the battery for the ten mins and see if this does anything. Thank you for your help so far. :)
 

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ML 270CDI 2002, BMW K1300S, VW POLO 1.9TDI
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I see ,well that explanes why that did not fix the Auto lights:D. It does not have auto wipers just the headlights. I have also never had the windscreen replaced. They do work sometimes,I found on here someone had the same bother but never found the cure to this. I will try and disconnect the battery for the ten mins and see if this does anything. Thank you for your help so far. :)
I have exactly the same problem as you on my 2002, ml270cdi.
Since changing the battery i havent been able to get the auto lights to work (nor the headlights when unlocking) they worked perfectly before i changed the battery. I have been advised that the 'coding' may have been lost and re-coding the auto lights might work?

Please keep us updated, as i will.
 

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02 ML320 06 ML500
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17,000 Posts
As of MY 02 the Auto Lamp feature came into being and something must turn that feature on, hence the Sun Sensor.

Reading the exterior lighting wiring diagrams for MY 02+, it does not show the Sun Sensor. So what you must do first is remove the sun sensor.

At the two wire connector, check the Brown wire for ground (supplied by the AAM) with a DVOM. If ground is present, cover the top of the sensor with a dark rag and then check the Blue wire for ground; giving it a few seconds to react.

Post back with results.
 

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2004 CLK 240 Coupe
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11,377 Posts
43sqd - you may wll be correct...:)

But my WIS references show something different.:confused:

1. Wiring diagram for air conditioning PE83.40-U-2000-99GJ for Model 163 as of 1.9.02, with code 491 (US version) & 581(a) air conditiong, automatic climate control. This shows B32 sun sensor.

2. Wiring diagram for windshield wiper PE82.30-U-2000-99H for model 163 as of 1.9.00 with Code 491 (US version)
This shows B38 rain sensor (only).

3. Wiring diagram for windshield wiper PE82.30-U-2000-99I for model 163 as of 1.9.00 up to 31.8.01 with Code 491 (US version)
This shows B38/2 rain and light sensor.

Maybe this anomaly is the difference between US and non-US versions of W163...

Where the windshield rain/light sensor is used (on other models) the screen must be very clean or spurious wipes will occur. I expect this also to affect the auto lights feature.
 

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02 ML320 06 ML500
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43sqd - you may wll be correct...:)

But my WIS references show something different.:confused:

1. Wiring diagram for air conditioning PE83.40-U-2000-99GJ for Model 163 as of 1.9.02, with code 491 (US version) & 581(a) air conditiong, automatic climate control. This shows B32 sun sensor.

2. Wiring diagram for windshield wiper PE82.30-U-2000-99H for model 163 as of 1.9.00 with Code 491 (US version)
This shows B38 rain sensor (only).

3. Wiring diagram for windshield wiper PE82.30-U-2000-99I for model 163 as of 1.9.00 up to 31.8.01 with Code 491 (US version)
This shows B38/2 rain and light sensor.

Maybe this anomaly is the difference between US and non-US versions of W163...

Where the windshield rain/light sensor is used (on other models) the screen must be very clean or spurious wipes will occur. I expect this also to affect the auto lights feature.
Yes, I agree, but if there is no rain sensor installed, then the Auto Lamps have to rely on the Sun Sensor to turn them on.
 

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Discussion Starter #8
Keyhole and 43sqd,I thank you both very much for looking into this matter. As I said this model does not have Auto wipers only Auto Headlights. I have all ready replaced the sun sensor so I think I can rule out a fault with it,but I will have a look at the wires. What I would like to know is there a relay or fuse which might be to do with the sun sensor,or auto headlights. It's also odd that alphonsohall changed his battery and had the same bother,so I will disconnect the battery for ten mins and see if this resets it. I will let you all know if I have any luck. Many thanks to you all,I am new to any Forums and so far I am so pleased there is some nice people willing to help.
 

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ML 270CDI 2002, BMW K1300S, VW POLO 1.9TDI
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Keyhole and 43sqd,I thank you both very much for looking into this matter. As I said this model does not have Auto wipers only Auto Headlights. I have all ready replaced the sun sensor so I think I can rule out a fault with it,but I will have a look at the wires. What I would like to know is there a relay or fuse which might be to do with the sun sensor,or auto headlights. It's also odd that alphonsohall changed his battery and had the same bother,so I will disconnect the battery for ten mins and see if this resets it. I will let you all know if I have any luck. Many thanks to you all,I am new to any Forums and so far I am so pleased there is some nice people willing to help.
As above, many thanks.

I've since tried disconnecting the battery (for 1 whole day) but its made no difference, i still dont have auto lights, etc
 

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2002 ML270 CDI
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I've never had auto lights working on my ML270. In auto mode it just turns them on and off with the ignition.

What I wanted was auto on when it gets dark, like when you go through a tunnel etc. tehn off again. But no, its just on all the time the ignition is on, so I never use it.
 

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ML 270CDI 2002, BMW K1300S, VW POLO 1.9TDI
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I've never had auto lights working on my ML270. In auto mode it just turns them on and off with the ignition.
The pdf file in 43sqd post #5 (ref auto lights) states that the default for the sensor if it becomes faulty is 'ON', so perhaps, in your case, it is the light sensor causing the lights to stay on in auto position.
 
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