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Discussion Starter #1
Hi everyone. I've been having a small issue with my w203 2001 c320.

My low beams (and rears) are going on every time I turn on the key, sometimes they turn off upon engine start or after some driving, DRL are off by default and I have the switch set to off when this happens.

When switched to automatic they turn off (depending on ambient light) and work ok, so i guess the light sensor is fine.

Otherwise the car has been running well, it has 75k miles, had the alternator and battery changed a couple of months ago at a trusted MB service and no other electric problems.

Just hope i don't have to replace the SAM module, since those are way too expensive here!
 

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I don't think it's the SAM because it's two different SAM's: the headlights are on the front, and the tail lights are on the rear. If you leave the switch in auto mode, do they still come on? If not, it might be a faulty switch. Another indication of that being the culprit would be if the interior backlights (cluster, switches, radio, etc.) are also on with the switch in the off position.
 

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Discussion Starter #3 (Edited)
Hi rodney, thanks for the tips!

Just went down to the garage to check. Tried every combination and this is what I get.

Lights switch off, contact on = Low beams & rears on, no interior lights on dash or buttons.

Lights switch off, engine on = same as above, sometimes they go out during a drive (30 minutes or so).

Lights in auto (dark), contact on or engine running = lights on, dash lights up after 15 secs, I hear a relay when interior lights turn on.

Lights in auto (w/light), contact on or engine running = lights on, regulator goes up and down (2 or 3 secs), then off. Dash lights never come on.

Lights on, key in, contact or engine running = everything on as it should. Dash comes on instantly.

Everything off, after drive = lights stay on for a couple of secs after I remove the key, no dash lights. No relay sound when they come off.

Remove battery, wait for a couple of minutes, restore power. Everything works well for a couple of on-off cycles, then it starts playing up again.

Seems like a stuck relay or a bad ground but I don't know where or which relay is it.

Edit: just forgot, the car has factory self leveling xenon lights without projectors
 

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There's no relay - it's just the SAM that control the lights. Check fuses 50, 62 and 63 in the front SAM (i.e. fusebox under the hood)
 

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Discussion Starter #5
Hi Rodney, checked the fuses and they are ok, it even has the factory ones by the looks of it. None of them is burned out and the slots seem to be clean.

I'll try to get my hands on a light switch this week and test it on the car. I don't see anything wrong with it but who knows... :confused:

I'll update once I test it.

Thanks for the help!
 
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