Soon after my "Light Sensor Visit Workshop" fault kept coming up intermittently, it started mingling with the "Undervoltage Consumer Defective" fault. It turns out I had a bad alternator which killed the battery. I replace the battery and alternator, and then the ODB at the dealter said it was excessive current draw coming out of the overhead electronics unit (where intermittent wiper, and light sensors for "Auto" lights position is. Here's the dealer rip-off:

They stated they can only replace the entire OEM unit in the ceiling...cost? $750 for the part only. I refused to buy it, but I did find out that now after the alternator/battery replacement, when I have the light switch in "Off" or "Auto" that the lights are always on, and when I switch it to manual "On" position, the lights go OFF!!! Does anyone know about this issue?

 

Hey, I am receiving the "Light sensor visit workshop" malfunction on my W209 2003 CLK. However I have noticed that myautomatic windscreen wipers do not work now and Ihave to alter the speed of the wipers manually. The other thingI have noticed is that when I leavemy lights on automatic they work as they are suppose to e.g. come on when it gets dark but when I unlock my car my lights do not automatically come on as they used to. I have checked the setting on the computer to program the lights to come on whenthe car is unlocked and that seems to be turned on.

Does it sound as though the light/rain sensor needs replacing? Is this simple enough to do myself or will I require it to be done at the garage. Would 1st litebe able to send me the diagrams of how to replace it? Also how much would I be lookingfor a new light/rain sensor in the UK?

Thanks

 

The Light/Rain sensor is in the top centreof your windshield (windscreen) in front of your rear view mirror. Pop the plastic cover off and you will see the unit.Release theretaining clips on the right and left sides to remove the unit. Unclip the electrical connector and remove. Reverse order for install.
You may not have to replace the sensor. There is something about recoding the rain/light sensor for different shading in the windshield. That's only if thewindshield has been replaced with a different shade of glass. This coding I believe has to be checked and or programmed with "STAR Diagnossis" to the "overhead control panel module".
Troubleshoot everything before you buy this sensor. I knowit is about $270 in Canada.
Happy New Year! and good luck.

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I have had this problem "light sensor" fault followed by dead battery, and I did hear the motorized noise coming from the front end after I turned the car off, this never happened in the warm weather only after it began to get very cold.

 

I am currently having this issue myself.

I started getting an intermittently dead battery. So I went into the dealer and he said to call MB roadside and it would be cheaper to change battery. So I did. Then I kept getting the "light sensor visit workshop" intermittently. So, I was hooking it up to a trickle charger and only driving it sparingly. Finally, I was coming home from work and got the "light sensor visit workshop", then the "under voltage", then the "Alternator visit workshop" and finally something about engine temp (cant recall what it was.

When I called the dealer, they kinda gave me the run around. So I googled and got a local shop who services MB. They replaced the alternator for $650 and a fuel filter which was a fault code they picked up.

I thought it was done and over with. And now once again, I started getting the "light sensor visit workshop" message again. I have the lights turned off of auto and it goes away. I got here by googling for the message. I want to try and change the light sensor myself. If I am going to keep this car, I absolutely have to learn to work on it myself.

 

here is a picture looking up at the sensors on a2002 C240







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I too have this problem - also yesterday on starting in the cold morning air, the battery appeared flat and car would not turn over - I got the light sensor error - holding the key in the start position for about 10 seconds then started the car. I went to work and all was fine. I went to start the car at lunchtime (car was left for about 3 hours) and again it started after about 10 seconds and I got an ESP error. Also the fuel gauge went to almost zero even though the tank was 3/4 full. Car then started and all was ok.

Went to start the car to go home 4 hours later and it started ok - fuel gauge was back to normal. I have taken it to my local non MB repair centre - they say they have reset the faults and it should all be ok now. If it goes wrong again they say they want the car overnight. But I think I will go replace the battery if that happens before taking it back to them. I will post my conclusions here when I find out what it is.

 

So I got the car back from the garage - they reset the codes (they listed more than I have seen saying there was a cylinder misfire error and other nasty sounding issues - yet this morning the "Light Sensor Error - Visit Workshop" reappeared (spent £66 quid for nothing) so am going to replace the battery this weekend and see if that fixes it.

 

Update, I replaced the light sensor, but still got an intermittent error code. About2 weeks later the car would not start. The battery is original (2002 C240) and was down on electrolyte. Filled it to the proper level with distilled water. The error code stopped after I put the distilled water in. But a week later, the car was having starting problems again. After an overnight charge itwas still taking6 amp continiously and had an open circuit voltage of 10.5 VDC; definitely bad. Ijust replaced the battery today.

I am not getting an error code since I put distilled water in the battery andam getting about 10ma current draw on the new battery. However, the overhead light panel circuit board (A203 820 1401 8G69)is makinga slightelectrical buzzing noise.

Lets see what happens.

 

I went to my local friendly Tyre and Battery place and they replaced the battery with a new one (not an easy task - its a snug fit) - all problems are now resolved - I've been using the car for a week now and no more errors.....