SLK Brake light

Hi
I've got a 2003 (R170) SLK 320 and the left brake light has failed.
I've changed the bulb and swapped the bulb & holder with the one from the right cluster and still the left bulb is out. I've removed the cluster and can see nothing wrong with it.
So my question is: Do the rear right & left clusters have the same wiring? My idea was to take both clusters out and sit them in the boot connected to the wrong side then (as long as the connectors are the same) if the fault is with the cluster the same light will fail, however if the fault is with the wiring then the fault would move to the other cluster.
Or are there any other diagnostic methods that'll help me to pin down the faults location?
The fault was intermittent but has now completely failed suggesting to me a loose connection that has finally fallen off - back of the fuse box perhaps?
Thanks DaveO.
Reply to
DJO
wrote:
Pity
No problem, use my trusty multimeter
Yes, the "Light Failure" bulb is lit.
I'm aware of the known problem with the clusters and have been shown a faulty one from another SLK at a garage and mine looks fine however I'll have a go with some switch cleaner on the connector and the contacts on the cluster, I might try adding some solder to where the bulb holder contacts the cluster if power is getting there.
Many thanks DaveO.
Reply to
DJO
wrote:
OK I tested the cluster connections with the multimeter and there is nothing wrong with the cluster. At the other end there is a single fuse for both brake lights and as one works then it cannot be the fuse.
Logically this only leaves the cable or a connector somewhere although were car electrics are concerned "logic" does not seem to apply so I'm open to any suggestions about either locating the problem or circumventing it.
I could run a cable from the right cluster to the left cluster but I need to know how the sensor that works out a bulb has failed works, if there is a separate circuit for each bulb then a new cable run would put no drain on one sensor and a double drain on the other sensor which would not be good, however if the sensor just looks for the drain of 2 bulbs on one circuit then there is no problem with circumventing the problem with a short wire run.
Many thanks DaveO.
Reply to
DJO
Wouldn't it be sensible to test the cable end at light and work towards the power source testing joints as you go with the switch activated at the peddle /
Reply to
atec77
If I knew the path the wiring loom takes and can work out access points then yes but everything is packed kinda tight in the SLK but I'll see if I can track down the other end of the cable run.
Thanks DaveO
Reply to
DJO


Perhaps injecting a tone from a cablers toner set and track it should be easier
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On short cables that are bundled, this can be difficult. It may be advisable to turn the power on the toner to a low setting.
Reply to
Sal M. O'Nella
Thanks everybody, I've found the problem and it was really stupid and almost entirely my mistake although the Merc main dealer made the same error (and charged me for the pleasure) so I don't feel too bad about it.
Once again, thanks for all your help.
DaveO.
Reply to
DJO
wrote:
OK yes it was something along those lines, I mixed up two of the lights and was looking at the wrong socket, also the side light on the other side had blown so the bulb fail light was coming on for that as well masking the other issue.
Pretty stupid really but an easy mistake to make and when it came back from the Merc dealer with the suggestion that a new cluster (a snip at £168 + VAT) would fix the problem when I was sure the cluster was OK (and I was right) it only added to the confusion. Anyway now I know better and can laugh at idiots who make the same sort of mistake - Ha ha! :-)
DaveO.
Reply to
DJO
Merc assist has proven to be clueless so not surprised to hear they suggested an expensive and useless option , door latches on my E320i were faulty and their suggestion would cost a fortune . Simply put replacing the system with a cheap aftermarket electric solenoid system and aftermarket alarm was the sensible thing to do and made the car much more secure .
Reply to
atec77

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