SLK Third Brake Light not working?

[00slk]

This has been showing up on the dash as not working and today I decided to have a look. At first it was an intermittent fault. Checking it and was found to be working, not it doesn't work. Disconnected the plug and refitted, still nothing so I removed the third brake light so I could put it across a battery to check to see if it was the light or something else. Picture of test, hopefully someone will be able to tell me if what I did is correct to test this light off the car. Should the brake light have worked by feeding a live wire to one of the terminals and earth the other terminal?
I'm not great with electrics
Many thanks in advance

 

[JayJay1]

Mine did the same a few weeks ago w203 after pressure washing in the wrong place message appeared saying malfunction so i pulled it out ran a supply from spare battery as car cuts supply if malfunction exists, so did same as you but i will say Leds are polarity conscious as in + & - have to be on correct terminals try from yr battery on terminals then reverse if nothing order a new one i did £20 ebay installed 10 mins works a treat

 

[00slk]

Mine did the same a few weeks ago w203 after pressure washing in the wrong place message appeared saying malfunction so i pulled it out ran a supply from spare battery as car cuts supply if malfunction exists, so did same as you but i will say Leds are polarity conscious as in + & - have to be on correct terminals try from yr battery on terminals then reverse if nothing order a new one i did £20 ebay installed 10 mins works a treat

Thank you JayJay1 (my wife's name sake, she JayJay too lol)
Yes I did try both sides of the terminals on the light, looks like a replacement is in order then

 

[JayJay1]

Thank you JayJay1 (my wife's name sake, she JayJay too lol)
Yes I did try both sides of the terminals on the light, looks like a replacement is in order then

Good stuff Lemme know how you get on

 

[00slk]

Good stuff Lemme know how you get on

Hate to say this but the brake light has fixed itself without any help
Been working good since the o/s rear tyre got a puncture yesterday
New Third Brake Light has just turned up in the post

 

[JayJay1]

Hate to say this but the brake light has fixed itself without any help
Been working good since the o/s rear tyre got a puncture yesterday
New Third Brake Light has just turned up in the post

There are areas in the boot where cables can get worn through and damaged had this with my number plate light did you move things around in boot spare wheel ??? Maybe worth asking all people if this is the case that doesn't explain why battery didn't light it up poss bad solders on their way out in light ?? Give it time may go completely then new one will come in handy

 

[JayJay1]

There are areas in the boot where cables can get worn through and damaged had this with my number plate light did you move things around in boot spare wheel ??? Maybe worth asking all people if this is the case that doesn't explain why battery didn't light it up poss bad solders on their way out in light ?? Give it time may go completely then new one will come in handy

All should read slk

 

[00slk]

All should read slk

Thanks JayJay1.

I did pull and prod at the wires around the hinges but nothing tell tale came out of it.
It wasn't working but yesterday on her wa home she phoned to say the Brake light malfunction didn't come up on the dash, so she asked me to check it when she go in, which I did and saw that it was working. That is when I noticed all the air had escaped from the tyre.
I think you maybe right that it is on the way out this light and now that we have a spare it'll most likely stay working. Murphy's Law

 

[JayJay1]

Good luck hope all goes well

 

[00slk]

Up Date: SLK third brake light has fixed itself 2 days after ordering a new third brake light last month
I have been waiting for the Missus to say it's not working again but no such luck, it is working well, so now we have a spare part for an SLK just in case it stops working
Just wish r230's fixed themselves

 

[wagdog]

On another site (can't remember which one), this intermittent problem is described as common and usually can be fixed by resoldering the two input connections to the printed circuit board inside the third brake light housing Original post described where to drill a 12 mm hole to access pc board connections then, after repair, blocking the hole with a grommet. My memory is that the hole was made about 1/3 the distance along the back of the black plastic from the right hand side, inboard from a moulding mark.