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Marty, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 55016
Experience:  Bosch Certified Master Technician with over 35 years experience in the automotive industry.
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got a problem with my tail lights on ml says bulbs are

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got a problem with my tail lights on ml 420 says bulbs are out & indicator wont work checked bulbs ,there ok tried swapping sides thats ok ..brakelight bulb on offside is staying on with ignition off & key out at a loss help please
Hi, you did not post the model year of your ML but based on your description of the problem I am assuming that you have a W164 chassis ML. If that it the case it sounds like your rear signal acquisition module is faulty. The module controls the rear lights on the ML. It is not unusual for water to find it's way into the module and short it out causing the erratic rear light operation. I've attached a picture of the module below. Let me know if you have any questions.

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Customer: replied 4 years ago.

hi, its 2007 ml 420 & when you take panels off as shown there seems to be a lot of detached modules etc..


Yes the picture shows the car somewhat disassembled in that area. The arrow is pointing to the rear SAM.
Customer: replied 4 years ago.

thanks ,does unit have to be programmed by mercedes ?


Yes it does, unless you purchase a used one from the same model car with the same part number.
Customer: replied 4 years ago.

lol just my luck there wont be many second hand ones about,you any idea of cost of new one please ..


They sell new for around $500. I'd get the part number off the old module and run a search on eBay. You can often find used ones there.
Customer: replied 4 years ago.

if thats US dollars & not UK pounds think i can handle that ..

Yes that US dollars :-)

Let me know if you need anything else.

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Customer: replied 4 years ago.

most certainly will ...