lotusmbw

Hello All,

I have a 2008 MB C300 4Matic. This is a more than 2 month old problem in my car and each mechanic gives a different reason and it is still not fixed. The right side front and back parking (yellow) lights randomly come on and go off. Sometimes when I stop and lock the car, they do not go off. Then I restart the car and move the headlight switch here and there and stop the engine and then they go off - this might take more than one iteration some times. My neighbours have come to tell me that these lights were coming on and off in the night. The battery gets drained and I am not able to start the car in the morning. I have bought a jump starter to manage till it gets fixed. But it is big pain to do it everyday. The first mechanic i went to, made me buy a brand new battery from the dealer. It did not solve the problem. The second mechanic ran the scanner and said that it needs SAM modules. The third mechanic also ran the scanner and tells me that the rear fuse box is defective and needs to be replaced. The car is now pretty old with a lot of kilometres (I am in Canada). I do not wish to spend too much money. Any suggestions on how to fix this problem.

I am also thinking of buying an OBD2 scanner to check the fault codes myself so I can post it here and maybe get some ideas and advice. I would appreciate if there are any suggestions about what might be some good OBD scanners to consider which would detect these electrical issues as well. Thanks in advance.

KelseyR

I have a 2009 Mercedes c350 and I’ve been having the same issue. It is also my right side lights. I’ve replaced my battery and had all the fuses checked. The dealership told me that it’s common that wires in the taillight melt and cause grounding issues. But I can’t find anything with that. Another suggestion was that the connectors in the taillight may also be bad.. but my issue is that I’ve replaced a headlight, all side markers, and all parking lamps, and none will come on. But maybe your problem could be melted wires like my dealership said. Good luck!

Russell Ormerod

It sounds like you own a w204 series?
if so its an easy fix. replace the headlamp switch and be happy

lotusmbw

Thank you to KelseyR and Russell.
I read somewhere else also about the headlight switch. I am wondering if there is a way to confirm the solution before spending a lot of money in getting it replaced and then finding out that it did not fix the problem. Is it possible to get the headlight switch out of the dashboard and leave it kinda hanging. I can take out the cable and disconnect it every time I park the car. If that works for a week without draining the battery, then that might mean that the headlight switch replacement will fix the problem.
Does my above idea make sense? Can somebody knowledgeable please confirm it or suggest some other way of doing it?
It is next to impossible to find used parts of Mercedes. Dealer parts are expensive. I am not very competent with fixing things myself so I have to depend on mechanics. So I am just thinking of ways to fix the problem without too much expense.
Thanks.

Russell Ormerod

You come for advice then you doubt what you get.
Good luck with your methods of diagnosis they will surely lead you up the wrong path.

lotusmbw

I am surprised and sorry that you have taken it the wrong way!

As we can see from the above posts, I am faced with 5 alternatives:

1. change battery - I spent $400 on this and it did not fix the problem
2. melted wires
3. change SAM modules
4. change rear fusebox
5. change headlight switch

I had read about the headlight switch solution more than 2 months ago when I first had this problem. I have mentioned it to all the 3 mechanics I have been to and they all completely ignored my suggestion. For somebody like me, who does not do any repairs on his own, this is not an easy situation. So it is not about doubting anyone or any advice. I have the fullest appreciation and respect for everyone and every suggestion and advice. I am only trying to solve the problem in a cost efficient manner.

Thanks again to everyone!

Russell Ormerod

Non of them know what they talking about!
a battery! Neve
a SAM not impossible but never seen it.
Melted wires. Nope! All 4 lights come on.
headlamp switch! Very common fault.. just tap the switch or knock on it and the lights will go on and off.
I can show you all the headlamp switches i have replaced in my workshop.
its a stupid design inside using a potentiometer read into an ADC then the output goes onto LIN bus
designed to fail.
find a guy with star diagnose and look at the switch inputs to the SAM. You will your problem there.
Good luck

Jeraldlklee

thank you for your answer. Im having the same issue with my wife's car. I'll purchase a headlight switch.