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ml270 2003 w163.
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7 Posts
Discussion Starter #1
noticed my brake lights have stopped working. Ive checked fuse 15 and swapped the relay. Bulbs are ok so i went looking for the switch. Its gone.
there is a hole and no switch. No abs lights are on only the very occasional BAS/ESP light normally when i go through a puddle. It does go back out.
So. Has someone nicked my switch or has it decided to leave the comfort of its slot.? Is there 2 switches. The cruise control still works so im in a right cafuffle....regards upfront Dave
 

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2003 ml500, 2004 ml350
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931 Posts
This is why you need to add your year and model to your Avatar.

Your don't say what year you have;
Earlier models switch is on the brake

Later on the booster.
 

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ml270 2003 w163.
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7 Posts
Discussion Starter #3
noticed my brake lights have stopped working. Ive checked fuse 15 and swapped the relay. Bulbs are ok so i went looking for the switch. Its gone.
there is a hole and no switch. No abs lights are on only the very occasional BAS/ESP light normally when i go through a puddle. It does go back out.
So. Has someone nicked my switch or has it decided to leave the comfort of its slot.? Is there 2 switches. The cruise control still works so im in a right cafuffle....regards upfront Dave
 

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Dallas, Texas
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7,140 Posts
Sometimes in 2003 switch was omitted. Brake lights depend on switch inside brake booster.
 

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ml270 2003 w163.
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7 Posts
Discussion Starter #7
just braved the wind for a look under the bonnet. On the servo is a switch and one under the master cylinder. Which one is the brake light switch. Ive also been googling and i cant find a replacement for either of these components. Anyone got a part number.?
 

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Switch A7/7s1 is inside the booster. Not replaceable separately. Need to scan traction systems. Failure will also cause shifter stuck in park.

Here is relevant thread.
 

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ml270 2003 w163.
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Discussion Starter #11
Update on the brake lights. They still dont work. New switch turned up and its wrong. Ive got no cables under the dash for the switch. Ive now physically pulled out and inspected every fuse and bulb. Everything is fine. So how on earth do you repair this switch issue. Is it the pressure sensor on the master cylinder.?? does that work the brake lights. Its a shame but the car will be scrapped if i cant repair the lights. Mot is due in 3 weeks and i cant use the damn thing with no brake lights. Mercedes really thought this one through.
I moved away from Landrover but feel im swaying back because of theyre simplicity.
 

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Update on the brake lights. They still dont work. New switch turned up and its wrong. Ive got no cables under the dash for the switch. Ive now physically pulled out and inspected every fuse and bulb. Everything is fine. So how on earth do you repair this switch issue. Is it the pressure sensor on the master cylinder.?? does that work the brake lights. Its a shame but the car will be scrapped if i cant repair the lights. Mot is due in 3 weeks and i cant use the damn thing with no brake lights. Mercedes really thought this one through.
I moved away from Landrover but feel im swaying back because of theyre simplicity.
Using volt meter with brake pedal depressed check for power at both ends of fuse F1f15.

Take clear picture of front fuse box.
 

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2003 ml500, 2004 ml350
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Dave did you look at the diagram it is not the highlighted part #10.
But part #9 which is inside the booster Mercedes does sell that switch but Witek said "Not replaceable separately".

Some parts even though you can rebuild them are not worth it. On Many American car the power steering pump fits into and is surrounded by the reservoir when it leaks though you can buy a rebuild kit, the failure rate is very high for a DYI, it's not worth it

I believe the switch is called a brake pedal travel switch.

If yours is indeed bad, you are one of the few unlucky ones, because your would be the first I have heard of.
 

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But part #9 which is inside the booster Mercedes does sell that switch but Witek said "Not replaceable separately".
Part #9 is diaphragm position sensor and it is available as separate part 163 540 12 17.

2020-02-16_105301.png
 

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2003 ml500, 2004 ml350
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Witek

Their is massive amounts of confusion on 03 and up brake light switches. So much so that one 03 service manual I have access to says it is on the pedal! Google for a video on how to replace it on an 03 every video says it's on the pedal.

But we all know 03 and up there is just and empty hole.


So there are 2 switches that I know of on the booster/ master cylinder.

002-542-84-18-64 Pressure Sensor, Sending Unit.

and
  • 163-540-12-17
  • Other Names: Sensor, Sending Unit, Stop lamp Switch, Position Sensor, Sender Unit
On 03 and up w163 it is the later that also serves as the tail light switch? Correct or is there a third switch?

I don't have access to either ml right now but can't Dave easily unplug the switch jump it and see if the brake lights function?
 

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2004 CLK500 (Wifes), (2) 2005 ML500SE, 2004 ML500, 2000 ML320, 2002 ML320
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61 Posts
I have attached a couple of items I made for testing brake light problems on 2003 to 2005 W163's only, for my son to use. Hope they clear up
some of the confusion. This is not a simple system to troubleshoot.

Witek's post #10 is correct, the brake release switch (A7/7s1) is part of the brake booster.
2003 to 2005 W163's ESP Control Module (N47-5) is mounted on the front side of the ABS pump behind the left headlight.
 

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I have attached a couple of items I made for testing brake light problems on 2003 to 2005 W163's only, for my son to use. Hope they clear up
some of the confusion. This is not a simple system to troubleshoot.

Witek's post #10 is correct, the brake release switch (A7/7s1) is part of the brake booster.
2003 to 2005 W163's ESP Control Module (N47-5) is mounted on the front side of the ABS pump behind the left headlight.
Interesting. Where those documents come from?
 

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ml270 2003 w163.
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7 Posts
Discussion Starter #19
Sounds like a whole load of work for a simple job on any other car. I.ll scrap it and thats the mercedes love gone. Ive ran landrovers for years and kept em on the road with minimum fuss. My mercedes has had a high pressure pump. New fuel lines 5 injector seals a new alternator. A steering angle sensor. new auxilary belt and tensioner.

in 8 months. now the simplest repair is sending this to the junk yard...im done with ML,s. What a stupid system.
 

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What caught my attention is part number for k6 listed in those documents. 002 542 11 19 is most common relay used on any Mercedes so I know part number by heart.
So, I go to Xentry Portal to look at that relay for my ML350 and sure as hell it lists two versions of k6.

002 542 29 19. Blue colored relay with contacts 30/87 normally closed.

002 542 29 19.png



And 002 545 11 19. Black relay with 30/87 normally open.

002 542 11 19.png
 
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