binary420

C230k Tail Lights Turning off - no brake lights
Hello, I'm newly registered here, this being my first post, however I have been coming to these forums for years and truly appreciate all the help and advice readily available here.
Im having a really strange problem with my tail lights on a 2002 C230 Kompressor (coupe) which i havent been able to find anything with this exact issue though ive found similar, im hoping to get some advice or clarification as to what could be causing this issue.
I recently replaced my battery and understand the rear SAM getting blown is pretty common, however the symptoms dont sound to me like they could be caused by the SAM being blown.
My fuel pump is working perfectly fine, which i know is powered by the same SAM unit. My issue is with the tail lights and some orher lighting related problems.
When I put my key into the ignition and turn to the on position. i hear the fuel pump relay click, and no issue there, but no tail light running lights come on.
Then when i press the brake and clutch, still no brake lights,
only after i crank the engine, the vrake lights come on. I'm able to press the brake pedal, the top stop lamp gets brighter, i release, it dims, i press, it gets brighter
ok, now the strange thing is within 2 or 3 seconds of the engine starting, the brake lights seize to function.
no light at all.
not dimmed, not bright, nothing. but if i turn the engine off and repeat, it works again for 2-3 seconds consistantly.
also along with the brake lights, the turn signals and hazard button work intermitently, but not consistently like the brake lights, its much more rare that the turn signals will work. maybe 1 in 10 times i start the engine.
also, I heard relay B clicking on and off repeatedly, so I unplugged it (relay 2 terminal 15R) then i was still hearing clicking from relay E or maybe it was F i dont remember where I unplugged it from, but that was either relay 1, terminal 15R, or rear window heater.
I started the car up and the lights were working good for about 45 seconds and turn signals were functioning great! But 45 seconds later and again, all tail lights off.
the running lights which are in their own little housing ehich are a tiny little bulb, those ones are working jyst fine they stay on as they should, and dont turn off like the brake lights.
also for good measure i should note that I also unplugged relays G and H which control the filler cap locking / unlocking, no joy.
I dont have the money to take it to the dealer, and not well versed on how the scanners work or which one you need for mercedes, I understand you need a "star diagnostic scanner" but who has that that I can use for a reasonable price, and would pulling the codes from that scanner be able to pinpoint what is going on?
I think based on my research this far, Im going to get alot of people saying I need a new rear SAM or maybe new front SAM (or both)
but I feel like that might be too drastic a step at this point, since the lights are still functioning like they should, and fuel pump is working fine, the lights are just ****ting themselves off after a few seconds and i have no idea how to fix it. is there a way to check the internal fuses in the SAM or check the unit beyond just testing the blade fuses?
I have a multimeter and volt meter but dont know where to go from here
Please, if anyone has information/ advice they can share on this topic, I will greatly appreciate it

JKehler

Dude. Your SAM is kaputski. Jut replace it yourself or pay $800 for someone else to do it.

binary420

But if that is true, why does my fuel pump still work?
And why do the lights still work but only for a few seconds?

Russell Ormerod

When you know how a Sam functions internally you will understand why they do what they do, you can spend days looking for your issue but in the end you going to need a new Sam!

There are many many different circuits inside a Sam, and I have repaired many, in far worse state than yours, and never ever do the fuel pumps not work, and no there are no fuses inside to test, only driver ICs that love to die or partially die. Sometimes the logic circuit before the driver fails too,
Sometimes the the Flash in the mcu is corrupt!

Many things fail, But fuel pump always works

Good luck!

Andy Lord

I had turn signals, windshield wipers, door windows and a number of things intermittently working or not. I replaced every Sam unit, pse pump, all window regulators, all fuses and pre tested relays. Followed every all data procedures and only found faults within can bus lines.. took it to 3 mechanic shops who were unable to find issues using better equipment providing detailed info. Autohaus who claims to specialize in Mercedes said any attempted repairs would be a part replacing mess that wouldn’t guarantee a solution. They did, however, say if they unplugged a rear window motor it would allow everything else to function properly, but you would not be able to roll the back window up or down anymore. Seems ghetto, but actually worked.. it may not solve your issue, but is easy to pull off a door panel and unplug the connector to the motor. Even if you tried both sides, it take less than 30 min and depending on the headache it’s caused you; it may be worth a try.. I hope this helps and wish you all the best of luck!