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Giving up !!

A

amazighman

Active Member
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Apr 22, 2016
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747
Car
CLK 430
Hi all

After a lots of head scratching and guessing I went ahead and replaced the rear SAM on my W203 C220 CDI coupe 2006 , as I have no brake lights , only substitute lights come on all the time and no warning messages about bulbs.

Unfortunately the new SAM didn't solve the problem I am close go throwing the towel and selling the car.

Replaced both rear brake light bulbs with halfords P21W , still no joy.

Cleabed contacts on the holders nothing , I dont even get a warning message that brake bulbs are out.

Could it be the Halfrauds bulbs causing the issue or the bulb holder itself?

Tested and no voltage is going to the brake light bulbs socket when brakes applied...

Thanks
 
Before giving up, I would start with basics, what does your I Carsoft say. , did it start with 1 bulb then both after you changed bulbs ? Have you checked fuse ? Any other issues that may suggest break light switch.

Have you looked at wiring diagram to trace break light wires and test, made sure connector blocks are ok

Iv not had this issue but from reading lots of post on electrical issues, it does seem bulbs can be an issue and need to be correct ones for car, have you for a few quid tried gen MB bulbs that dealer supplies using your vin

Usually with electrical I found what happens first is biggest clue to root cause and once you start messing or changing parts it confuses matters as we asume new part is correct and working.
 
The middle brake light and substitute ones work , so if there is a switch it should be ok , I thought these cars dont have a brake light switch , instead they have a sensor at the brake master cylinder/servo
 
I have in the past had issues with cheapo Halfrauds bulbs being a tad undersized and not fitting the holders correctly causing issues; but that wouldn't account for you having no volts at the bulb holder OP.
 
I will try a better set of bulbs , may be Ring brand.
Before this problem started , I had a warning light brake light bulb left couple of times , which then disappeared and took the brake lights with it

I dont know what to do about the switch , i can test it while someone is applying the brakes .. that should tell if its ok ...

Could the bulb holder be faulty? The puzzling thing is that no warning messages on dash...
 
Last edited:
If the SAM sees a fault in the cct or lamp/s it removes the feed to that / them and initiates the substitute lamp/s.
The problem there is once the SAM has timed out to substitute you're looking for a feed that has been removed by design.

I would be v surprised if you don't have a brake light switch above the brake peddle. But as the LED is illuminating I would be surprised if that were the issue. These switches do have double contacts though but don't see why one contact wouldn't be used to tell the SAM to illuminate all brake lamps.

Lamps or lamp holders would be my thoughts.
 
Thanks m80.
I will order some bulbs and a bulb holder , I will try and report back
 
Earths all good ?
 
Just showing the OP the brake light switch that doubles as the switch to tell the ECU that the brake is depressed so the gear selector will move. Not a hall sensor just a bog standard mechanical switch , bit like this.


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Reactions: m80
Petrol Pete said:
Just showing the OP the brake light switch that doubles as the switch to tell the ECU that the brake is depressed so the gear selector will move. Not a hall sensor just a bog standard mechanical switch , bit like this.


www.ebay.co.uk

Brake Light Switch A 006 545 10 14 For MERCEDES-BENZ A-Class W168 168.031 168.13 | eBay

Find many great new & used options and get the best deals for Brake Light Switch A 006 545 10 14 For MERCEDES-BENZ A-Class W168 168.031 168.13 at the best online prices at eBay! Free delivery for many products!
www.ebay.co.uk
Click to expand...
Sorry , looked at 360 , its upside down , I now see the plunger .
 
I'd get your bulbs from the main dealer.
I once had to replace a rear brake light bulb on my then W210. The one I bought from Halfords didn't work as the pin positions are very slightly different on a Merc compared to a standard brake light bulb.
 
+1 as others have said. Once it sees the wrong resistance, it will turn off the output. You can try measuring for voltage each time you cycle the key to see if its even detecting the right resistance or if possible the donor SAM you bought is faulty? This is quite a common fault.
 
alexanderfoti said:
+1 as others have said. Once it sees the wrong resistance, it will turn off the output. You can try measuring for voltage each time you cycle the key to see if its even detecting the right resistance or if possible the donor SAM you bought is faulty? This is quite a common fault.
Click to expand...
Possible.
I will try with new bulbs , then holder , then maybe another sam albeit i think both sam units are fine...
 
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