stupid question - trailer lights

[redneck joe]

but its me and its electrical...

no trailer lights. working just fine last time i checked them on the truck but that is gone now using the car which i used to bring home from MN. only used a couple three times since and the wire stays tucked up in a storage area in the trunk.

to determine if car side just tester pointy thing to the green plug, turn on some lights and stick the other pointy thing into the other holes and look for voltage?

 

[alldodge]

In most cases if none of the lights are working with a 4 pin plug it's the ground (white wire)

https://www.etrailer.com/faq-wiring-4-way.aspx

 

[Pmt133]

I agree. It's almost always the ground.

 

[Alumarine]

This tester is good for testing the 4 wire connector on the vehicle.
This is just an example. They are widely available.

https://www.etrailer.com/Electrical-Tools/Brophy/F4CT.html

 

[tphoyt]

I have had mice chew the wires in the trailer frame several times. Always a good place to
look if tow vehicle checks out good.
And agree on the ground.

 

[Captain of the Double G's]

The most stupid question is the one not asked

 

[Scott Danforth]

Does your truck have separate trailer light fuses (mine does)

 

[redneck joe]

truck is gone, this is car and afternarket added so assuming no. everything worked when i used the truck.

 

[Jeff J]

The exposed pin on the car side should be the ground. Check for voltage at other pins against it. If that works then the trailer ground is the first place to look when nothing works.

I have also had the fixtures lose ground individually along with badly corroded bulb sockets. Maybe the most common failure I see is the cheap clip on wire splices the trailer manufacturers like. Uncommon for these items to all go bad at the same time.

Occasionally I run into a situation where someone has removed the ground wire from the trailer expecting the ball to provide the ground. It will make intermittent contact at best.

 

[Ifishmuskie2]

I always run the ground directly to each light. I just did a trailer. All wires are covered to prevent mice attacks. I use led and don’t unplug when launching.
Use a meter to check vehicle side.