Rear Taillight Not Turning On
Thread Starter
Newbie
Joined: Sep 2025
Posts: 3
Likes: 0
2008 gl450
Rear Taillight Not Turning On
I got a notification the other day that my passenger taillight was out. I went and ordered a new one off of Amazon and replaced the burnt one, but it wouldn’t turn on. After trying with a new set of bulbs the problem persisted.
I then used my multimeter to check fuses and all seemed okay, I also attempted to apply power via the probe straight to the light connection and it turned on, so it must be something stopping the power from reaching the bulb. I had the rear SAM replaced by dealership about two years ago, and upon further inspection there was no moisture or corrosion on the module.
I plan to try an oem bulb from the dealership, if that doesn’t work then i’ll attempt replacing the PC board, and if the problem persists then i’ll try checking out the brake switch or continuity of the wire.
Has this happened to anybody else?
I then used my multimeter to check fuses and all seemed okay, I also attempted to apply power via the probe straight to the light connection and it turned on, so it must be something stopping the power from reaching the bulb. I had the rear SAM replaced by dealership about two years ago, and upon further inspection there was no moisture or corrosion on the module.
I plan to try an oem bulb from the dealership, if that doesn’t work then i’ll attempt replacing the PC board, and if the problem persists then i’ll try checking out the brake switch or continuity of the wire.
Has this happened to anybody else?
Last edited by 2008gl450driver; Sep 25, 2025 at 10:02 AM.
MBWorld Fanatic!
Joined: Jan 2010
Posts: 3,119
Likes: 784
NGL450 w/EORP, S550
Yes, and it’s almost always due to water intrusion in the D- pillar either coming from the sunroof or the tail lamp seals.
have you looked at the light assembly in detail?
if you’re spare tire area is dry in the SAM is undamaged than that would be it.
have you looked at the light assembly in detail?
if you’re spare tire area is dry in the SAM is undamaged than that would be it.
Thread Starter
Newbie
Joined: Sep 2025
Posts: 3
Likes: 0
2008 gl450
By the assembly do you mean the PC board or the housing?
Thread Starter
Newbie
Joined: Sep 2025
Posts: 3
Likes: 0
2008 gl450
The assembly and pc board look dry and don't have any signs of water entering in. I get a carwash twice a week so I don't want to rule out the possibility.
MB Dealer quoted me ~$10 per bulb and ~$92 for a replacement board.
Hopefully using an OEM bulb will solve this problem. I don't want to buy the board to find out that that isn't the problem neither
MB Dealer quoted me ~$10 per bulb and ~$92 for a replacement board.
Hopefully using an OEM bulb will solve this problem. I don't want to buy the board to find out that that isn't the problem neither
MBWorld Fanatic!
Joined: Jan 2010
Posts: 3,119
Likes: 784
NGL450 w/EORP, S550
If you were trying to use an aftermarket LED bulb that usually doesn’t go well with the rear SAM.
$10 for a oe filament bulb vice going straight to $92 board is prudent troubleshooting in increasing order of cost.
$10 for a oe filament bulb vice going straight to $92 board is prudent troubleshooting in increasing order of cost.
