Lights won't turn off in any position, draining battery, help!

[Slkroadsterr]

Hi I have a 2001 slk 200 kompressor that I'm trying to fix and get back on the road. The car has been sitting for a number months, Just replaced the oxygen sensor that was causing a fault code previously, but everything was running and working the way it should.

Put a new battery in and noticed that when I turn the car off the headlights turn on. Tried putting the light switch in all different modes and didn't make any difference. Even took the key out and the lights were still on, even after 30 seconds. Doesn't seem to have an automatic mode. Then after taking it for a short test drive the high beam turned on and didn't react to the high beam switch on the stalk. Have disconnected the battery and looking for the root cause.

Been doing some research and it's doubtful it could be k40 relay module, didn't check the fusebox, but doubt a blown fuse would turn everything on. Is there a separate light relay in this model? Could anybody give me some advice as to what the issue could be or if you've had a similar problem? Would be greatly appreciated!

 

[grahamcol]

This seems to be a very strange issue. I'm wondering if you should now reconnect the battery and see if the issue simply goes away. My thinking is that maybe after a period of disconnection the system may reset and revert to normal operation. Good luck with this.
Oh and welcome by the way. If my suggestion doesn't work l expect one or two other members will chip in with some alternative suggestions. The car may need a Star diagnostic session in order to establish the cause of the strange behaviour.

 

[sonic]

Welcome, if the light switch is off & the lights are on it must be back feeding from somewhere else.
I would be having a close look at all the earth points, good luck.

 

[Slkroadsterr]

Hi all, thanks for your replies. I have been connecting and disconnecting the battery every couple of days and the problem persists. I haven't touched anything on the car so no idea where the grounding issue could happen. Battery is connected the same way the old one was. I'm kinda stuck and I need to sell this car ASAP, anybody else have any issues like this before?

 

[Slkroadsterr]

Hi anybody who's reading this thread, I took the car to the garage and they immediately told me that I was looking at £300 to replace a relay module, and that it could be the k40 but they would need a few hours labour to determine which one. I swallowed the figures and decided to keep trying myself. I pulled out the k40 relay module following a YouTube video and it looks brand new, no burn marks or solder crossing paths, thought I'd check this one first but seems it's not the one. At least I saved an hour or so labour by doing it myself. Could someone tell me which relay module controls the headlamps? And maybe where I can find it? Thank you in advance!

 

[Slkroadsterr]

Hello again, after checking the k40 module and it seemed brand new, the next thing I thought it could be was the indicator stalk, according to the guys at the garage, as both sides headlamps turn on when I turn the car off, so it couldn't be both headlamp relays that are gone, as they are separate, but they all connect into the indicator combination switch. Anyway, long story short, I replaced it after taking off the steering wheel, buying more tools and removing the lower dashboard. To my dismay, the problem still continued. The garage would have charged me 400-500 at this point after all this work and parts, and it's still not the cause of my issue. Is there anybody on this forum who has experienced a problem like this before? Not sure where to look next, garages are scratching their heads and I need to get this fixed on a budget!