issue with trailer turn signal/brake lights

[blueblaster8]

Question regarding my 1997 ranger trail trailer. After observing some poor work done by the previous owner, I decided to replace light fixtures and all of the wiring. After getting everything installed, the running lights are working without any problems, however the brake lights, nor turn signals are working. Prior to running the new wires threw the trailer, I set everything up at the back of the vehicle and everything was working as expected, brake lights and turn signals included. Now after installing everything, it appears that there is voltage being dropped, there is still just enough to light the running lights, but not quite enough to power the brighter brake and turn signals. All of the grounds are fixed in the same places as they were prior, when everything worked well. The only thing that makes sense is that there is a ground issue dropping voltage, however I am not sure that the running lights would work if the grounds were bad. I have attempted to ground everything in different places to no avail. I am certain that everything on the vehicle side is good, indicated by the fact that I am getting voltage to the actual light fixtures, just not enough, and there is in fact full voltage coming off the vehicle. I have attempted to clean the ball and hitch to potentially better/assist in grounding the trailer, without any luck. The only difference from testing everything at the back of the vehicle, and after running all the wires to the actually light fixture locations is the grounds, but I can't seem to figure out the problem. Anybody have any thoughts? Thanks in advance!

[5keepers2]

Drive it around the block a time or two and see if everything starts working as it should. Sometimes the ground just has to connect between vehicle and trailer.

[CatFan]

Drive it around the block a time or two and see if everything starts working as it should. Sometimes the ground just has to connect between vehicle and trailer.

Absolutely the wrong answer. The ground is a wiring connection and driving won’t change it. If driving around changes anything it just points out that the trailer is wired wrong.

[Ed R]

The ball and hitch has nothing to do with a good ground to your trailer. You should be able to plug your trailer & vehicle wiring together without the vehicle and trailer being coupled. All lights, marker, stop, directional should work as intended. If they do not work when plugged in in this manner, you do not have a hard wired ground from vehicle through the plug to the trailer. If you have a swing away tung, be sure the main ground is grounded behind the swing away at the trailer.

[5keepers2]

Absolutely the wrong answer. The ground is a wiring connection and driving won’t change it. If driving around changes anything it just points out that the trailer is wired wrong.

I have owned around 15 boats/trailers including the one I have now and all of them were wired to ground through hitch. White wire from truck not connected and white wire on trailer not connect. Yes I know you can connect the white wires and have a ground to vehicle. It is done both ways and both ways are common! I don't know how op did it and they don't say! Just trying to help!

[CatFan]

I have owned around 15 boats/trailers including the one I have now and all of them were wired to ground through hitch. White wire from truck not connected and white wire on trailer not connect. Yes I know you can connect the white wires and have a ground to vehicle. It is done both ways and both ways are common! I don't know how op did it and they don't say! Just trying to help!

No. The hitch is never part of the ground unless it is wired wrong. No trailer is ever made without a ground wire because grounding through the ball does not work.

[5keepers2]

No. The hitch is never part of the ground unless it is wired wrong. No trailer is ever made without a ground wire because grounding through the ball does not work.

Walk through a parking lot at a good size ramp on a Spring Saturday and see how many white wires on trailers are not connected.

[CatFan]

Walk through a parking lot at a good size ramp on a Spring Saturday and see how many white wires on trailers are not connected.

Just because some people are dumb doesn’t make it right.

[billnorman1]

You can ground through the ball if it makes you happy, but don't forget you are also supposed to grease that ball to prevent it from unscrewing the ball from the hitch. Depending on that ball for an electrical connection is unwise, and it can lead to intermittent lights or brake system solenoid issues.
The post sounds like a weak ground issue. Running lights draw less current than brake or turn signals so a bad ground may allow running lights but not brake lights. A good way to test the ground is take the hitch off, and run the positive meter lead from the trailer frame to the meter, and the negative lead to a good ground on the truck. With the brake or emergency flashers on, the trailer ground should not exceed +1 VDC.

The actual issue with a weak ground is not a voltage drop, but a voltage raise, on ground.

[wmitch2]

You DO have a ground issue. YES, the trailer ball can be used as a ground, BUT, is not advised and could be your problem if you are doing this. !! Start first by checking with a test light at the plug in on the vehicle. Turn on your Lights, and Emergency Flashers AND put it in reverse ( with the engine NOT running). Attach the Clip of the tester to the Ground pin (should be the bottom right pin on a round round plug, and the exposed pin on a flat 5 pin plug) and then test to see that each other pins light or flash. If all are working properly, then the problem lies in the trailer. NOW, if you're using the trailer frame as your ground, you need to run a wire from the ground on the plug to EACH light. This should solve your problem. IF it doesn't, you may have a "Fixture" (light) that is shorting out. You'd have to disconnect each one and test it. The frame is never a good ground. There are too many things such as, loose hitch, rusted trailer ball, swing away, or removable tongue etc.