Trailer Light Grounding

[MinnnesotaGuy84]

Trailer light grounding seems like it ought to be straight forward but I'm stumped.

Here's what I know:
I had a guy at the shop test the cord coming off my truck and it it lit up his tester. I have new wiring throughout the trailer that worked when I wired it up, turn signals, brakes and running lights:everything working. Suddenly they stopped working, so after shineying up the tongue, I reattached the groundwire to ensure a good connection. Now I get dull brake lights but no turn signals.

I purchased a multi-meter and I have limited understanding of its use. I set it to ohms and touched both leads to the light sockets and got readings. Also I touched it to the connection of the ground on the tongue and got a reading. My readings have consistently been 0.9 to 1.1 when set on the lowest ohms setting on the multi meter.

Any ideas on where my problem is or other troubleshooting tips.l

 

[rasimmo]

I think you are going to get continuity through the light because that is how the circuit works. Power through the light to ground. Your problem may be in the plug on the trailer. I had a similar problem with trailer lights and the pins were either bent or corroded in the plug. I changed it out and problem went away. Good luck, trailer wiring can be agrivating at times.

 

[BobRip]

I acts like a bad ground. Try voltage test as follows. Turn on the light. They are dim, right. This means that not all of the voltage is getting to the lights. Leave the lights on. Set your meter to Dc volts. Measure the voltage from the ground of the towing vehicle to the ground on the trailer. This should be very low, less than one volt. Check other parts of the circuit such as between the towng vehicle 12 volt line and the positive at the bulb. All light do not have to be on. Pull one bulb and check the Voltage between the center terminal and the towing vehicle 12 volts. I hope this helps.

 

[dstig1]

Am I the only one that wires a trailer by grounding back to the plug, and not using the frame as a ground? Yes the frame is attached to ground for the "return path of last resort" but the primary ground circuit is all wired, not counting on the frame.

 

[RandyT]

Had a bad ground on my 12 ft landscape trailer a few years back. the poor ground backfed the lighting circuit and fried the radio, antilock brake module, and blew the backup light fuse. (backup light circuit terminated at truck and doesn't even go to the trailer). I rewired the trailer and ran a ground wire from all the lights back to the plug.

 

[Sutol]

I agree that it will be the plug, could be damp that causes the problem, put a new one on

 

[bigdad]

I had a snowmobile/dump type trailer once that I had a real crazy light problem with. Even though I had a good strong 13 volts (Hummmm no load....) at all of the sockets ..... the bulbs would not light. After some serious head scratching I figured out that where the frame hinges for the dump was not carrying any CURRENT to fire the bulbs. I put a jumper from the tongue to the rest of the frame around the hinge and I had lights.

Lesson: Run a seperate ground. Also, get LED lights and never worry about corroded sockets again.

 

[pat32rf]

Separate ground right back to the plug.
Solder and dielectric grease on all joints before heat shrinking them.
Never hurts to run a separate ground wire for the trailer brakes if it has them. Join it to the main ground at the front of trailer somewhere.
Fasten all wiring up out of harm's way when finished.....
There comes a time when it can be easier to re-wire than find the problem, especially if someone else did the original wiring job...

 

[Soundguy]

most testers do not provide a realistic load.

I like lamps with at least 2 ground paths. frame and copper wire.

with frame and wire grounds tied at the coupler.

I like a good ground for the socket ont he truck, plus I add an aux ground wire with a QD plug at my bumper or GN/5th wheel hookup, that attaches to that common tied ground I have at the trailer. IE.. quite a bit of redundancy.. however.. turn signals don't make the brakes bump on and off..

can't have too much ground where needed..

soundguy

Trailer light grounding seems like it ought to be straight forward but I'm stumped.

Here's what I know:
I had a guy at the shop test the cord coming off my truck and it it lit up his tester. I have new wiring throughout the trailer that worked when I wired it up, turn signals, brakes and running lights:everything working. Suddenly they stopped working, so after shineying up the tongue, I reattached the groundwire to ensure a good connection. Now I get dull brake lights but no turn signals.

I purchased a multi-meter and I have limited understanding of its use. I set it to ohms and touched both leads to the light sockets and got readings. Also I touched it to the connection of the ground on the tongue and got a reading. My readings have consistently been 0.9 to 1.1 when set on the lowest ohms setting on the multi meter.

Any ideas on where my problem is or other troubleshooting tips.l

 

[Willl]

I set it to ohms and touched both leads to the light sockets and got readings.

I'm thinking it should of been set for voltage, the readings you got where most likely erroneous.

Easy mistake for first users.