Truck harness or trailer harness issues.

[Kelpike]

This is a runoff from a previous post I had. I'm not getting brake lights or blinkers on my camper. From a suggestion on my previous post I checked the terminals of the harness on the truck. Yellow was 0 with truck running, 12.5 with brake pressed, jumped up and down with left blinker on. Green was 0 with truck running, 12.5 with brake pressed, jumped up and down with right blinker on. Red was 13.4 with truck running, 13.2 with brake pressed. Brown was 13.4 with truck running, 13.2 with brake pressed. Is my truck harness wired wrong?

[BarabooBob]

I would try using jumper wires on the trailer plug to verify proper operation. First thing to remember when looking at the trailer plug is that everything is backwards so either draw your own diagram or at least remember it.
The first thing to do is make sure that your trailer connection is getting a good ground. Using a VOM set for continuity, touch one probe to the ground (position 1) on the plug and touch the other probe to an unpainted spot on your frame. If you don't have continuity between the plug and the frame, you will always have problems with your lights. Grounding problems are almost alwyas the cause of trailer light problems.
Using a good battery-use jumpers to attach the negative to the ground, jump from positive to blade 5 (yellow) and your left brake/turn signal lights should come on.
Move the positive jumper to blade 6 (green) and your right brake/turn signal light should come on.
Move the jumper to blade 3 (brown) and your marker lights and tail lights should lights should come on.3

[opnspaces]

Kelpike wrote:
This is a runoff from a previous post I had. I'm not getting brake lights or blinkers on my camper. From a suggestion on my previous post I checked the terminals of the harness on the truck. Yellow was 0 with truck running, 12.5 with brake pressed, jumped up and down with left blinker on. Green was 0 with truck running, 12.5 with brake pressed, jumped up and down with right blinker on. Red was 13.4 with truck running, 13.2 with brake pressed. Brown was 13.4 with truck running, 13.2 with brake pressed. Is my truck harness wired wrong?

Your truck is wired correctly. the turn signal and stop lights share the same wires. So in effect you have two brake light wires, (a left brake light and turn signal wire and a right brake light and turn signal wire).

Kelpike wrote:
Yellow was 0 with truck running, 12.5 with brake pressed, jumped up and down with left blinker on.

This is correct operation. Yellow is your left turn signal and brake. It should read 0 when the truck is running. If you step on the brakes it will go to a steady 12v. Put on the turn signal and the voltage will jump up and down as if the light is blinking.

Kelpike wrote:
Green was 0 with truck running, 12.5 with brake pressed, jumped up and down with right blinker on.

If you are referring to blade 6 in the diagram this is correct operation. Green is your right turn signal and brake. It should read 0 when the truck is running. If you step on the brakes it will go to a steady 12v. Put on the turn signal and the voltage will jump up and down as if the light is blinking.
If you are referring to pin 7 in the center then you are wired incorrectly.

Kelpike wrote:
Red was 13.4 with truck running, 13.2 with brake pressed. ?

Red is battery power. It is behaving as expected.

Kelpike wrote:
Brown was 13.4 with truck running, 13.2 with brake pressed.

Brown is taillights also called the running lights. It should have power when the truck lights are on. It is behaving as expected.

But don't confuse these colors with the wire colors in the umbilical or the trailer. The wire colors are probably different. You really need to take your meter to the trailer and check what each wire does regardless of the color. Remember, the wire colors may lie, the meter will not.

[mr_andyj]

The truck plug chart Tom posted showed number 7, center pin, as green. This does not seem right to me, but according to the chart green is reverse. I would research a little to double check the colors of wires...

[BurbMan]

ajriding wrote:
That the green (backup) did anything is an issue, it should only do something with truck in reverse.

If the green the OP is talking about is the dark green for right stop/turn, it sounds like it's working as it's supposed to.

[BurbMan]

Sounds like the truck is OK, you confirmed you have voltage on the left stop/turn (yellow), the right stop/turn (green), the charging line (red) and running lights (brown). If there were any fuses blown on the truck you wouldn't have seen those voltages at the connector.

The most common problem is a bad ground in the camper lights. Take off the lenses and look at the bulbs and sockets, check for corrosion on the ground connections. That's the reason you're not getting any lights at all, because all tail/stop/turn functions require a good ground.

Also look on the frame under the batteries or where the umbilical cord terminates at the camper. Usually the white ground wire in the 7-wire cord is grounded to the trailer frame, and then the frame is used as a common ground throughout the trailer. Take those connections off of the frame, clean them up and apply some di-electric great when re-attaching.

[ajriding]

Keep in mind that the colors on the truck will not match the colors on the trailer. Some do, some do not. You need two color charts, one for TV one for trailer.

According to the Chart Tom posted, assuming it is correct....
You mention some wires jump when brakes or blinkers are on (brake light is the blinker light) then two things could be going on. 1. the voltage for all the trailer wiring is coming from one small source and the extra power demand is robbing power from all others so is making it jump. Unlikely since there is no "demand" given the trailer is not plugged in. 2. a bit of a short, not enough to short and blow a fuse, but just enough to draw down power, maybe a bad ground, or two positive wires touching, barely...

That the green (backup) did anything is an issue, it should only do something with truck in reverse.

I would first assume the wiring is correct, and check for bad wiring instead of wrong wiring.

Is your truck wired with factory trailer wiring or is it spliced into the trucks rear light harness wires?

Your voltage ranged from 12.5 to 13.4, and there really should not be a voltage difference in an open circuit. Seems they should all be 13.4. If you had lights connected then a lower voltage would means one circuit has more draw than the other, but you are not even plugged into the trailer, so I would next assume that the voltage draw is from the truck itself. The truck brake lights would draw more power than the running lights or just one blinker (which is one brake light, not both).
Some trucks have a completely separate circuit for trailer wiring, but some share the circuit with the truck's lights. A shared circuit would make the voltage differences...

Sometimes the easiest way to fix electrical is to start over, run new wires. Tracking down electrical shorts or issues can take 10x longer than just redoing it all from scratch..

[Tom_M1]

Truck wiring is correct according to the following diagram:



You may have a ground problem.

[Lantley]

Could be a blown fuse in the truck. I had the same issue turned out to be a fuse in the truck (under the hood).

[JRscooby]

Sounds like a problem to me. The brake wire should be 0 until brake is pushed, then increase.