2004 140 WB
Low Standard Roof Cargo. I popped the tail light lamp assemblies off to begin wiring a Modulite relay unit for my trailer. Didn't get to install that because of rain, but learned some things. Someone had installed #1156 lamps (12V 21Watt) in each lower tail light unit. DC uses galvanized steel tracers to route the power on the light unit. I traced the traces and found a small jumper to the lowest lamp which makes it common with the tail light on the top stop/tail lamp. Having a 21 watt lamp in that position would make it look like the brakes were on instead of just tail lights. My 2004 manual doesn't give lamp numbers for replacement. The parts guy at the corner tried to sell me 21 Watt lamps again and was very insistent even though he was very (completely) wrong.
Here's what I recommend for a NAS aka NAFTA T1N:
Top Lamp = Brake/Tail = 1157LL 12V 21W/5W)
2nd down = Backup = 1156LL (12V 21W)
3rd Down = Turn = 1156LL (12V 21W)
Bottom Lamp = Tail = 5007LL (12V 5W) - Do not use more watts or it will appear that the brake lights are on.
License Plate Lamps = 6418LL (13.5V 5 W)
Note: The same lamp type for the license plate comes in 10 watt and even 20 watt versions. There is no place for the lamp heat to escape in your rear door. I strongly recommend using the 5 watt lamp I specify to keep the heating problem to a minimum.
Better yet is an LED replacement. My LED experience wasn't so great. Although maybe it is ok for other people.
https://sprinter-source.com/forum/showthread.php?p=390850#post390850
Wiring I found:
Tail/Park: L = Gray/Blk, R = Gray/Red
Stop: L =
Blk/Red, R = Blk/Red
Backup: L = Wht/Red, R = Wht/Red
Turn: L = Blk/Wht, R = Blk/Grn
Hope this saves someone some time if they need lamps or wire colors.
P.S. - Low Beam Headlamp = H7 55 watt, 65 watt, or 100 watt. I use CEC Industries H7 55w LL long life.
20100412 Edit: Below is a link that discusses trailer wiring options OEM vs aftermarket modules. Adding trailer wiring to a Sprinter is not a straight-forward process. If you have it installed, don't let 'em do whatever they want!!
Trailer Wiring OEM Harness vs. Light Module
https://sprinter-source.com/forum/showthread.php?t=7328&highlight=trailer+wiring