trailer lights

[CobyRupert]

It's not clear what people mean when they say use a ground wire instead of frame. Seems there are 2 possibilities:
1) Run a separate ground wire from each light instead of relying on the light contacting the frame as part of its mounting. Relying only on frame path requires paint be scraped where light mounts.
2) Other possibility is run a separate ground from the frame (trailer tongue) to the trailer's connector plug, and the vehicle's receptacle also has this terminal grounded to its frame, instead of relying on the connection through the ball (and the hitch /receiver)

I've only had to do the later.

Don't overlook that often there's a lot of paint and warning stickers on the removable draw bar (ball mount) that prevents a good conductive contact with the vehicles receiver when relying on the frame as a path. I've had to ground this off to get lights working.

Getting 20 volts is weird. Either something is going on with the trailer's battery somehow being in series the vehicle's (seems unlikely); or because of bad/missing connection (path), probably a ground, you're not really measuring across the battery.

(That is: If the battery negative terminal isn't connected to this reference (frame) that you measure from, the reading you get is meaningless; because you're only measuring voltage from the positive to the frame, but not the unknown voltage from frame to negative. This unknown voltage exists because the two are not connected.)

 

[PILOON]

One guy I know never bothers to wire turn indicators and uses standard extension cord (110 VAC 3 wire) to do so.
He claims the LEO's really don't care nor see that the turns don't work and actually the only 'give away' is non working brake lights or at night the markers.

On my trailer every lite works! and I use LEDs since potholes and filaments don't go well together.
Mind U with LEDs you need very good ground returns as the current is so low.

 

[downsizingnow48]

There are a lot of unknowns in the situation. If it was my problem to troubleshoot, I would start with the tow vehicle wiring. Make sure there is a continuous ground from battery negative terminal to the connector on the hitch. If the hitch was added on, it is almost certain that the ground wire just goes to the frame and can be compromised by rust or undercoating. If it is OEM it is continuous unless a previous owner made a modification, you never know, so everything has to be checked. Make sure all the connectors are wired properly and working at that point. Once the vehicle side of the connector is known to be functioning properly, then start the trailer troubleshooting.

 

[ugabulldog]

suprise suprise, it was the ground where rivet acts as ground to frame, or maybe it was the butt splices as I replaced a few also, (not sure where to 20v came from) Anyways, thank for all the help. I am going to run a ground wire from light base to inside of livestock trailer and ground to a tap screw into frame, .....rather than tie wires from all lights together into a common ground.

 

[RandyT]

It's not clear what people mean when they say use a ground wire instead of frame. Seems there are 2 possibilities:
1) Run a separate ground wire from each light instead of relying on the light contacting the frame as part of its mounting. Relying only on frame path requires paint be scraped where light mounts.
2) Other possibility is run a separate ground from the frame (trailer tongue) to the trailer's connector plug, and the vehicle's receptacle also has this terminal grounded to its frame, instead of relying on the connection through the ball (and the hitch /receiver)

I've only had to do the later.

Don't overlook that often there's a lot of paint and warning stickers on the removable draw bar (ball mount) that prevents a good conductive contact with the vehicles receiver when relying on the frame as a path. I've had to ground this off to get lights working.

Getting 20 volts is weird. Either something is going on with the trailer's battery somehow being in series the vehicle's (seems unlikely); or because of bad/missing connection (path), probably a ground, you're not really measuring across the battery.

(That is: If the battery negative terminal isn't connected to this reference (frame) that you measure from, the reading you get is meaningless; because you're only measuring voltage from the positive to the frame, but not the unknown voltage from frame to negative. This unknown voltage exists because the two are not connected.)

What is meant by separate ground wire is you run a wire from the vehicle plug ground terminal wire to each individual light. Either solder a loop connector to the end of the wire and attach it to one of the light mounting bolts which is normally the light ground, or if using LED, which normally have a separate white ground wire that is normally connected to the trailer frame or around one of the light mounting bolts, you connect your ground wire to it. That way you are not even using the trailer frame for the ground.

I have seen a bad ground on a trailer light actually backfeed through another light to find ground. Bad ground backfeeding the ABS system on the vehicle blowing the fuse. A bulb that was overturned and jumped the pin on a right rear turn signal activate all the running light on the trailer and the tow vehicle. Looked like you turned on the flashers but the sign marker lights on the trailer also flashed.

 

[PILOON]

I have a buddy that owns a storage facility and rents/loans trailers to help the clients move in. (he maintains 5) Nice perk!.
90% of his trailer lighting problems are from grounds!
The other 10% corroded connections.
We now solder all joints and run separate ground lines. 95% of the problems have disappeared.

On an aside most users are too lazy to crank up the hitch leg enough so many get damaged when they cross a curb.

 

[robertsa]

It's not clear what people mean when they say use a ground wire instead of frame. Seems there are 2 possibilities:
1) Run a separate ground wire from each light instead of relying on the light contacting the frame as part of its mounting. Relying only on frame path requires paint be scraped where light mounts.
2) Other possibility is run a separate ground from the frame (trailer tongue) to the trailer's connector plug, and the vehicle's receptacle also has this terminal grounded to its frame, instead of relying on the connection through the ball (and the hitch /receiver)

I've only had to do the later.

Don't overlook that often there's a lot of paint and warning stickers on the removable draw bar (ball mount) that prevents a good conductive contact with the vehicles receiver when relying on the frame as a path. I've had to ground this off to get lights working.

3) Wire it like you're supposed to with a proper ground from the vehicle frame to vehicle side connector and a proper ground from the trailer side connector to the trailer frame.

In this thread, I am seeing people working way too hard to fix a problem that is only a problem due to shoddy work. When properly wired and terminated, these problems don't exist. Adding solder and multiple terminations/splices due to running separate grounds to all the lights introduces more points of failure. You're doing more work while introducing more opportunity for faults.

 

[crazyal]

Do you have a small mig/ wire feed welder? Do yourself a favor and get some 1/4 stainless steel bolts and weld them to the frame near each light and near each axle (if you have brakes). Then run the ground from each light to the bolt. It'll never loose ground again. Counting on a metal contact touching the steel frame on a trailer will sooner or later fail as the bare metal needed for contact will rust. A number of trailer lights use the mounting studs as a ground as well. If possible I replace the steel bolt they use with a stainless bolt and then make up a short wire to connect the ground stud to the bolt I welded on the frame. While it's more work that running a ground wire to each light it's often easier on larger trailers.

 

[sandman2234]

Do you have a small mig/ wire feed welder? Do yourself a favor and get some 1/4 stainless steel bolts and weld them to the frame near each light and near each axle (if you have brakes). Then run the ground from each light to the bolt. It'll never loose ground again. Counting on a metal contact touching the steel frame on a trailer will sooner or later fail as the bare metal needed for contact will rust. A number of trailer lights use the mounting studs as a ground as well. If possible I replace the steel bolt they use with a stainless bolt and then make up a short wire to connect the ground stud to the bolt I welded on the frame. While it's more work that running a ground wire to each light it's often easier on larger trailers.
View attachment 551087

Interesting solution, to say the least! I am wondering why you stipulated a mig/wire feed welder? Any welder capable of welding stainless should work fine to weld the bolts, I would think.
David from jax

 

[crazyal]

Interesting solution, to say the least! I am wondering why you stipulated a mig/wire feed welder? Any welder capable of welding stainless should work fine to weld the bolts, I would think.
David from jax

I think it would be difficult to weld with a stick, being such small bolts. A TIG would work just fine but less people have them where as wire fed welders are pretty common now. As long as you paint it you don't even need to use stainless wire.