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2003 Mercedes ML350
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11 Posts
Discussion Starter #1
Hello guys I have two issues today..
1) My brake lights are not working so i ordered a new switch and i popped open the under dash and noticed that here wasn't a switch at all.
Is it missing? I tried looking for the wires but they were nowhere to be found..
ALL fuses are good.. checked already.
Did i buy the switch for nothing? help!

2) License plate lights aren't working either..Changed fuses, still nothing :(

2624488
2624489
 

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Dallas, Texas
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7,406 Posts
Here is long thread on brake lights issue.

 

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w163 02 ML500 W210 97 E50Amg w202 99 C230K w124 - need more space, time to build again
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2,412 Posts
As of 03, BLS is in the Brake Master Cylinder.

Please update your user cp.
click on your icon----> click on Account Settings---->
goto Account Details----> add vehicle details---->
add your make model YEAR ----> click save
 

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Registered
2003 Mercedes ML350
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11 Posts
Discussion Starter #4
Here is long thread on brake lights issue.

dam so i bought the switch for notthing ? :(
 

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Registered
2003 Mercedes ML350
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11 Posts
Discussion Starter #5
As of 03, BLS is in the Brake Master Cylinder.

Please update your user cp.
click on your icon----> click on Account Settings---->
goto Account Details----> add vehicle details---->
add your make model YEAR ----> click save
how to fix? so it's the sensor that's broken right?
 

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w163 02 ML500 W210 97 E50Amg w202 99 C230K w124 - need more space, time to build again
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2,412 Posts
how to fix? so it's the sensor that's broken right?
Dont know yet.
Check fuse #15 (under the hood in the fuse/realy box) with a test light or DVOM while someone steps on the brake?
 

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2003 Mercedes ML350
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11 Posts
Discussion Starter #9
Dont know yet.
Check fuse #15 (under the hood in the fuse/realy box) with a test light or DVOM while someone steps on the brake?
checked fuse already. it is good. I have a DVOM yes... but how do i use it to check?
TThe relay is also good bc i ttried other relays and it still doesn't work.

So it's confirmed my car has no switch?
 

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w163 02 ML500 W210 97 E50Amg w202 99 C230K w124 - need more space, time to build again
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2,412 Posts
checked fuse already. it is good. I have a DVOM yes... but how do i use it to check?
TThe relay is also good bc i ttried other relays and it still doesn't work.

So it's confirmed my car has no switch?
DID YOU READ THRU..... Witek's link he provided in post #2?
 

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Dallas, Texas
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7,406 Posts
checked fuse already. it is good. I have a DVOM yes... but how do i use it to check?
TThe relay is also good bc i ttried other relays and it still doesn't work.

So it's confirmed my car has no switch?
Do you have other warnings like BAS, ESP or ABS?
 

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Dallas, Texas
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7,406 Posts
yes i do.. they're on.
Sometimes randomly disappears.
You need to have it scanned for codes. Most likely failure is switch A7/7s1 mounted inside brake booster. That switch is not replaceable separately. Need to remove brake master cylinder, replace booster, pressure bleed entire brake system. Then do very thorough cleanup. Any trace of brake fluid will remove paint and any other rust protection.
 

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w163 02 ML500 W210 97 E50Amg w202 99 C230K w124 - need more space, time to build again
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2,412 Posts
I have. :( but it's confusing because i don't know how to test the fuses if they're working..
I was referring to where your BLS is located....

In that previous link, post #4, (already mentioned now in witek's post #14)
And in that previous link, post #6, (wallyo's comments on the component)
 

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2003 C320 coupe, 2000 ML320
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725 Posts
I have. :( but it's confusing because i don't know how to test the fuses if they're working..
Put your meter on OHMs.. touch the positive and negative leads together.. you should read something close to zero ohms.. Now pull fuse, .. put one lead to one side of the fuse and the other lead to the other side..you should read something close to zero ohms..just like if you were touching both leads together..

The in circuit test for 12v is:.. meter on DC volts.. negative lead to chassis ground.. positive lead to the exposed metal blade on the top of the fuse..You need to use a pin to get a good connection on the fuse.. the exposed part is too small to get the lead tip in there.. Step on brake.. you should have 12v on both sides of the fuse..
2624744
 

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2003 C320 coupe, 2000 ML320
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725 Posts
Wouldn't you know it.. I was looking out the window as the wife was pulling out the drive.. NO BRAKE LIGHTS...


It took me all of 10 minutes to diagnose the problem.. Bad brake switch.. Fortunately, I have an 2000.. switch on the pedal.. Piece of cake to replace.. The only reason I'm mentioning it is, .. It was posted that a tranny locked in park was a sign of a bad switch.. TRUE, but it's a two part switch.. The brake light part can fail (and you won't know it) but tranny park lock can still be good.. Step on the brake and you can take it out of park, like nothing is wrong..
 
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