View Full Version : Wiring my trailer lights.

05-23-2008, 10:26 AM
Well I am trying to button up my trailer and I am having a tough time figuring out how to wire my tail lights for the trailer to the 4 wire trailer stuff I have.

Here is what I have:

RV style 7 pin connector between truck and trailer
4 wire standard trailer wire for connects
FJ40 Tail lights.

Now I know the codes for the wiring:

White: Ground
Brown: Running
Yellow: L Turn and Stop
Green: R Turn and Stop

The FJ40 tail lights have:
One wire for break and one for running lights
Reverse light wire.
Turn signal wire.

The 7 pin connector codes are:
white = common ground
blue = electric brake
green = tail/running lights
black = battery charge (+)
red = left turn/stop
brown = right turn/stop
yellow - auxiliary/back up

How do I go about this? All I see is my brake lights and turn signals coming on all at once, everytime, how do I get around this or am I missing something?

Thanks this one has me scratching my head. :confused: :thumb:

05-23-2008, 11:02 AM
You get a trailer decoder box and install it on your 40 per the instructions. WFLLT.

05-23-2008, 11:21 AM
You get a trailer decoder box and install it on your 40 per the instructions. WFLLT.

Yeah you can get them at Checker, also topper/trailer shops. Should run about $20.

Are you going to use any of the extra connections from the round 7? If not I'm not sure why you wouldn't want to just run flat 4 on each, rather than require another pigtail adapter.

05-23-2008, 11:31 AM
Trailer brakes and battery charging?

05-23-2008, 11:43 AM
Decide what brand you might also use and wire accordingly. My GMC 7pin is not an industry standard when compared to Dodge or Ford. No one got together to make this a standard...they are all different.

05-23-2008, 12:52 PM
you gonna run a charge wire to the trailer?

05-23-2008, 01:29 PM
You get a trailer decoder box and install it on your 40 per the instructions. WFLLT.

Trailer decoder box?

Is that a junction box? I have one of those. Sorry, never heard of a decoder box, sounds cool.

Yes, I am using the RV 7 pin connector, it gives me some wiggle room for charging, brakes, auxilary lights and stuff down the road.


05-23-2008, 01:52 PM
found it, 3 to 2 wire adapter, thanks guys that is what I needed!


05-23-2008, 01:53 PM
Less fancy than it sounds. It takes separate signals for brake and turn (where the vehicle's turn signals and brake lights are separate) and combines them for trailer lights where the brake and turn are on the same bulb. AKA trailer light adapter.