SLK Brake light

[DJO]

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.

[Roland Franzius]

This post might be inappropriate. Click to display it.

[DJO]

On Wed, 24 Sep 2014 17:52:44 +0200, Roland Franzius

Post by Roland Franzius

Post by DJO
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.

They are differently wired.

Post by DJO
I've removed the cluster and can see nothing wrong with it.

Most probably the printed circuit to bulb connection is the reason.
Standar R170 problem.

Post by DJO
So my question is: Do the rear right & left clusters have the same
wiring?

No.

Pity

Post by Roland Franzius

Post by DJO
Or are there any other diagnostic methods that'll help me to pin down
the faults location?

Check voltage at connectors with pedal down (put a stick between padal
an seat).

No problem, use my trusty multimeter

Post by Roland Franzius
Change break light switch which often is faulty. It is a complicated
emergeny braking attempt detector but a rather cheap one.

Post by DJO
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?

No. Check the light control lamp in the instrument cluster. Does it
indicate a lamp failure?

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.

[DJO]

On Thu, 25 Sep 2014 09:49:16 +0100, DJO <***@phony.address.com>
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.

[atec77]

Post by DJO
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.

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 /

[DJO]

Post by atec77

Post by DJO
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.

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 /

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

[Roland Franzius]

This post might be inappropriate. Click to display it.

[atec77]

Post by DJO

Post by atec77

Post by DJO
Logically this only leaves the cable or a connector somewhere although

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 /

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

Perhaps injecting a tone from a cablers toner set and track it should be
easier

[Sal M. O'Nella]

Post by DJO

Post by atec77

Post by DJO
Logically this only leaves the cable or a connector somewhere although

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 /

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

Perhaps injecting a tone from a cablers toner set and track it should be
easier

======================================================

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.

[DJO]

Post by DJO
Hi
I've got a 2003 (R170) SLK 320 and the left brake light has failed.

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.

[atec77]

Post by DJO

Post by DJO
Hi
I've got a 2003 (R170) SLK 320 and the left brake light has failed.

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.

and it was ?

[Roland Franzius]

Post by atec77

Post by DJO

Post by DJO
Hi
I've got a 2003 (R170) SLK 320 and the left brake light has failed.

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.

and it was ?

Probably the wrong socket bulbs.

[DJO]

On Fri, 03 Oct 2014 12:05:03 +0200, Roland Franzius

Post by Roland Franzius

Post by atec77

Post by DJO

Post by DJO
Hi
I've got a 2003 (R170) SLK 320 and the left brake light has failed.

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.

and it was ?

Probably the wrong socket bulbs.

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.

[atec77]

Post by DJO
On Fri, 03 Oct 2014 12:05:03 +0200, Roland Franzius

Post by Roland Franzius

Post by atec77

Post by DJO

Post by DJO
Hi
I've got a 2003 (R170) SLK 320 and the left brake light has failed.

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.

and it was ?

Probably the wrong socket bulbs.

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.

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 .