Boat Trailer Lights -Help Please

eburd10

Cadet
Joined
Aug 25, 2018
Messages
8
New to the forum. Seeking some advice on boat trailer lights.

Just installed a new boat trailer light kit on my late father's old boat trailer. Kit included left/right back trailer lights and wiring harness. The standard trailer light kit from tractor supply.

Both lights are on when vehicle headlights on. With the running lights on, the left blinker does not work. The right blinker DOES work.

Also, when the running lights are on, when brakes are applied nothing happens on the left side (light does not get brighter) BUT on the right side the running light goes completely out.

So again, with running lights on, left blinker does not work, right side goes out completely when brake applied.

Any suggestions on what might be going on? I'm sure it's a ground issue.. I don't know how though. The wiring and lights are brand new.
 

Grub54891

Vice Admiral
Joined
Jun 17, 2012
Messages
5,908
Did you run the ground completely from the harness to each light? Never depend on the short pigtail on the harness. I always splice in and run a separate ground.
And also, Welcome to the forums!.
 

poconojoe

Lieutenant Commander
Joined
Sep 10, 2010
Messages
1,966
Are you sure it's not just a bad bulb? Or socket? Maybe a factory connection came loose from the socket? Just because it's all new doesn't mean it's good. Maybe it's the tow vehicle's wiring or the vehicle's plug. Can you try it on a different tow vehicle? It happened to me on my last vehicle. Out of the blue I had no right signal from the vehicle plug. I ran a new wire from the tail light and all was good.
 

Saddlehorse

Seaman
Joined
Aug 21, 2018
Messages
63
Sounds alot like a bad ground, have had that problem on several used trailers i have purchased in the past.
 

eburd10

Cadet
Joined
Aug 25, 2018
Messages
8
Did you run the ground completely from the harness to each light? Never depend on the short pigtail on the harness. I always splice in and run a separate ground.
And also, Welcome to the forums!.

Thank you!

Yes I just attached the pigtail from the harness to somewhere on the trailer. I checked the attachment point today and it looks like it should be getting good contact. I am not sure what you mean by running ground from harness to each light? Are you talking about running wire from the pigtail to each light and then back to the trailer to ground it? It's my understanding the lights are already grounded since they are attached directly to metal on trailer. Sorry, I barely understand how electricity works. I can splice wires of the same color together that is about it.

I think I may have had an issue with the tow vehicle. However, I am having a similar issue when hooked up to a new tow vehicle.

When hooked to a NEW tow vehicle....
Running lights OFF: Nothing works (brake lights do not come on when brakes applied, neither blinker works)
Running lights ON: Both lights on. Left/Right blinker lights work. BUT, when brakes are applied both left/right lights go out completely.

On the first tow vehicle I tried... With running lights ON the right blinker worked only, and only the right side went out when brakes applied. So I think something is going on with first tow vehicle wiring.... But nonetheless, still something messed up with new trailer wiring.

Thanks again everybody for the comments! Keep em coming!
 

appleo

Petty Officer 1st Class
Joined
Jul 19, 2012
Messages
388
DID you use those blue clip on connectors from autozone or did you solder?

Get a 20 ft piece of wire with alligator clips on each end clip one to tow car frame the other to the metal trailer frame rear by the tailights

Is one of your tow vehicles toyota?
 

eburd10

Cadet
Joined
Aug 25, 2018
Messages
8
DID you use those blue clip on connectors from autozone or did you solder?

Get a 20 ft piece of wire with alligator clips on each end clip one to tow car frame the other to the metal trailer frame rear by the tailights

Is one of your tow vehicles toyota?

No, I just used the wire nuts provided to attach the end of the wiring harness to the tag ends of the two lights. I mean I know both lights have power going to them because they come on when the tow vehicle lights are on. So connection there should be good. I planned to use butt splices and marine heat shrink to connect them. Just have wire nuts on there for now to make sure everything is working properly... Which it is not.

I am not sure what you are talking about with the 20ft wire.... From what it sounds like, I would just be gator clamping a piece of wire on the boat trailer and then at the other end clamping it on to my truck frame... Not sure what that would do? Doesn't sound like that would be completing the circuit or anything... Unless I am misunderstanding what you are saying.

Thanks!
 

eburd10

Cadet
Joined
Aug 25, 2018
Messages
8
DID you use those blue clip on connectors from autozone or did you solder?

Get a 20 ft piece of wire with alligator clips on each end clip one to tow car frame the other to the metal trailer frame rear by the tailights

Is one of your tow vehicles toyota?

No sir, neither tow vehicle is a Toyota.

Tow Vehicle 1: 2006 Chevy Silverado
Tow Vehicle 2: 1992 Ford F150
 

Grub54891

Vice Admiral
Joined
Jun 17, 2012
Messages
5,908
Yes I just attached the pigtail from the harness to somewhere on the trailer. I checked the attachment point today and it looks like it should be getting good contact.

What you should do, is splice that short ground pigtail to a wire, run it completely back to each light and secure it to the ground lug on each light. Never trust the frame of the trailer to carry the ground all the way through the frame. Been doing that way for years, the lights keep working.

The alligator clip wire is simply a test wire to see if you have a ground problem. I bet you do.​
 

poconojoe

Lieutenant Commander
Joined
Sep 10, 2010
Messages
1,966
As others have stated...usually when things are acting wacky you have a ground problem. A separate ground all the way to the rear, as suggested, is the way to go.

Also make sure you spliced onto the correct colors at each light. If they are reversed, some wacky things might happen. Back-feeding through the light...

Green = Right Turn
Yellow = Left Turn
Brown = Running Lights
White = Ground

​​
 

eburd10

Cadet
Joined
Aug 25, 2018
Messages
8
"splice that short ground pigtail to a wire, run it completely back to each light and secure it to the ground lug on each light. Never trust the frame of the trailer to carry the ground all the way through the frame."


Oh I see what you are talking about. I'll try that. Even though I'm not sure of the concept behind it I guess. Not sure oh grounds and circuits work to be honest. All I know is things need to be grounded. Lol

Will be next weekend before I can go back and mess with it. Thanks again! I'll try that and report back on how it worked out.
 

poconojoe

Lieutenant Commander
Joined
Sep 10, 2010
Messages
1,966
The concept of it... each light needs a positive and a ground for it to work.
You connected the ground from the plug to the trailer, so now the trailer frame is the ground.

Lots of things can go wrong by the time the connection is made at the light. Corrosion of frame, bad connection (electrically) between trailer tongue and frame, bad connection between frame and lights.
This is why he wants you to extend the ground wire from the front plug all the way back and connect it directly to the lights.
​​​
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,092
using a 12 battery at the trailer plug, white to ground, take a lead from the + battery and touch each of the other 3 . Green and Yellow should be bright, Brown should light the 2 running lamps in the taillight and any clearance lights
If this does not happen ,you have a ground issue and may have to run ground wires from the lights to the front of the trailer
 

Saddlehorse

Seaman
Joined
Aug 21, 2018
Messages
63
I never ground to trailer frame,they hardly ever work and when they do they dont last . Always run the ground from truck pigtail alway to the lights.
 

eburd10

Cadet
Joined
Aug 25, 2018
Messages
8
Ran ground wire from pig tail to bolt on trailer tongue. From same bolt ran another wire to one lug on passenger side trailer tail light. Was planning on running grounds to both sides as suggested... BUT everything started working properly after running to just one side.

Thanks again eveyone!

If someone could just tell me where the crappie are biting on toledo bend lake ill be good to go lol:joyous:
 
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