Hi this is for my bosses 1999 slk-230. Hes having a problem where the parking lights, and running lights are always on, even after he shuts down the car. Eventually the battery will die. We have tried replacing the headlight switch but instead of always being on it made the lights blink, if we unplug the gray harness from the back of the switch the lights do not stay on but the tail lights do not work. Is this a known issue or does anyone know whats wrong? Thanks

 

Does the interior light work correctly when set to "Door". i.e. automatically?
Does your security system (alarm) work cprrectly? Arm car with window open. Reach inside and see if alarm goes off when you open door from outside using inside handle.
Have you had any bulb failure warnings recently?

If so it is likely the PSE unit in the RHS boot under the floor in a foam bag.
Electrics on these cars are digital and you get very strange problems if the CAN (digital highway) has some form of short on it (often at the PSE) due to moisture / corrosion.

Stuart