2008 Mercedes C300 Headlights and License Plate Lights Flickering

Yakunan

i own a 2008 Mercedes Benz C300 (6 Cylinders 3.0L FI DOHC 183 CID) and i'm experiencing issues with my headlights. they randomly turn off and on without any specific pattern. sometimes they stay off for 10 seconds, other times for a minute. also, the lights that light up my license plate flicker too. i suspect these issues might be related, but i'm not entirely sure. any advice would be greatly appreciated.

edit:

after researching common problems with my car, i suspect the issue might be a faulty headlight switch, which looks to be a common problem. i'd appreciate confirmation from other reddit users if this seems likely, or any advice on how to diagnose the issue further. i can provide video and pictures.

thecardoc3

Having looked at the schematics the headlight switch is only an input to the steering column module which sends digital command information to the front SAM module. The license plate lights are controlled by the rear SAM module. While it's possible the switch could be failing this really needs to be tested and have the failure proven before someone starts replacing any parts.

BTW is this with or without the HID headlights, and is it the high beam, low beam or either that are going out? Plus, when the lights do go out does the "flash to pass" still work or is it not functioning either?

Yakunan

thecardoc3 said:

Having looked at the schematics the headlight switch is only an input to the steering column module which sends digital command information to the front SAM module. The license plate lights are controlled by the rear SAM module. While it's possible the switch could be failing this really needs to be tested and have the failure proven before someone starts replacing any parts.

BTW is this with or without the HID headlights, and is it the high beam, low beam or either that are going out? Plus, when the lights do go out does the "flash to pass" still work or is it not functioning either?

hi cardoc3,

thank you for the help. the car is equipped with halogen headlights, not hid. both the low beams and high beams go out at the same time. although the "flash to pass" feature still works, it doesnt function when the low and high beams are out.

~ yakunan

thecardoc3

With that information I can rule some things out, but not enough to really be useful. The switch is definitely still in play, but so is the steering column module and the front SAM (fuse/relay box left rear of the engine compartment). I can say you are not losing power from fuses 89 (125A) and 105 (100A) but that's really not very helpful at this point. You are going to need someone that has a scan tool that can access these modules to watch switch data inputs and output commands with bi-directional command capability.

Yakunan

thecardoc3 said:

With that information I can rule some things out, but not enough to really be useful. The switch is definitely still in play, but so is the steering column module and the front SAM (fuse/relay box left rear of the engine compartment). I can say you are not losing power from fuses 89 (125A) and 105 (100A) but that's really not very helpful at this point. You are going to need someone that has a scan tool that can access these modules to watch switch data inputs and output commands with bi-directional command capability.

thanks man, i appreciate the help