Trailer Lights

[cramer12]

Rewired a small boat trailer with new wire harness and lightfixtures. All lights work when headlights are turned on as well as turn signals, but the brake light doesn't work on one side. Could this something as easy as a bad bulb?

 

[Boomyal]

Re: Trailer Lights

Depends. On a two element bulb, the turn indicator uses the same filament as the brake lite. I would look for where the wire for that brake lite splits off from the trailer harness. You should have 4 wires at the plug. Ground, brake, left turn and right turn. So the one of the brake lite wires has to "Y" off the main harness.

 

[cramer12]

Re: Trailer Lights

The harness has 4 wires at the plug and if I'm remembering correctly, one wire used a spliter adapter for the side clearance light then continued to the back of the trailer for the rear clearance light. The other wire attached to the main connecter on the rear light. What color should the right brake wire be? I'll have to check my connection tomorrow. Maybe something pulled loose. Thought I followed directions, especially since the left side seems to work. It's not the truck. We pull two other trailers and don't have any problems with the lights. Thanks for your help.

 

[Boomyal]

Re: Trailer Lights

I made an error. You should have 5 wires. Tail lite, brake lite, left turn, right turn and ground. You should not be grounding thru the hitch, it is very unreliable and prone to light problems. All I mentioned before re the "Y" off the main harness to feed the second brake, lite still applies. <br /><br />The only exception to this would be some foreign vehicles need a converter because they use seperate brake lite and turn indicator bulbs. They do not have a built in brake lite interupt for when the turn indicator is on.

 

[cramer12]

Re: Trailer Lights

Oops. You're right. Five wires including the ground wire which I attached to the trailer tongue. I guess I'm not clear about what you mean regarding the "Y" for the brake light. Can you explain. Wiring definately isn't my thing.

 

[Boomyal]

Re: Trailer Lights

you have a main harness coming back from the male connector. It is either flat or round but had five wires in it. Identify the wire, at the plug, for the brake lite. Follow it to the rear of the trailer. Probably near the lite that the harness goes to first, there should be a wire that connects to the identified brake lite wire, that goes across the trailer to the other lite assy. Your problem is most likely at that connection. The "Y" is the connection point to the main harness for the 'other' brake lite. <br /><br />You should also run that ground wire direct to the car chassis, either thru the plug or independently. Hooking it to the tongue of the trailer and relying on the hitch ball to complete the circuit will eventually cause you hair pulling problems.

 

[Bass Runner]

Re: Trailer Lights

Coming from the tow truck there will be a ground white, two turn-brake wires one yellow one green figure out which is which and run one to each tailight, and a tail-running light wire which is brown, you will have to splice a extra wire into the brown wire so you will have one to go down each side splicing in running lights as you go, unless you have a really old tow truck there is no seperate brake and tail light wire the newer cars have a dual sys. one wire for brake and turn like i mentioned earlier. Sounds like you have the yellow or green connected to the wrong wire at the tail lights.

 

[Boatist]

Re: Trailer Lights

Cramer<br />Since you do not say I am going to assume a standard trailer setup that does not have seperate brake lights. If that is the case should be very easy.<br /><br />White wire - Truck frame ground to trailer frame ground.<br /><br />Brown wire - Truck clearance/headlights to all trailer clearance lights and tail light on left and right side.<br /><br />Green wire - Truck right turn/right brake light to trailer right turn/right brake light.<br /><br />Yellow wire - Truck left turn/left brake light to trailer left turn/left brake light.<br /><br />If your truck has seperate turn and brake lights then you need a adapter to wire the trailer. US trucks normaly do not need a adapter as left turn and left brake light the same light. Also right turn and right brake light the same light.<br /><br />See attached wireing<br /><br /> http://www.championtrailers.com/4 pole wiring dia.pdf

 

[Bass Runner]

Re: Trailer Lights

Everyone tries to make wireing hard, it's always been easy for me but i guess sometimes simple logic is hard to understand (if all else fails follow the directions) LOL

 

[cramer12]

Re: Trailer Lights

This has been very frustrating. Yes, I followed the directions on the wiring harness for the trailer and the lights are new. The wiring in the lights were color - coded with the trailer lights and the instructions that came with the lights verified that they matched the trailer wiring. the wiring harness has white-ground; brown- running lights; yellow -left turn and stop; green- right turn and stop. The tow vehicle is a 99 Expedition that we use for other boats without a problem. It has an adapter plug that converts the large plug on the expedition to the four wire flat plug on our trailers. (I also tried a different adaptor to see if that made a difference...no.) Last night I: changed the ground wire; changed the light bulb; switched the wires going to that particular light; bought another light fixture and tried that, still didn't help.<br /><br />The brake light does work, very faintly, without the headlights turned on. With the headlights on it does not. The tail light also has a side marker light and when the turn signal is working, it also flashes. The "working other side" of the boat, rear side marker light, does not flash. I haven't tried a volt meter, but the bad light isn't as bright as the other side. The last time I tried the turn signal (which usually works fine), the one trailer light was not flashing in harmony with the truck light. Flashing, yes, but at a different time than the truck.<br /><br />This was supposed to be an easy project with all new materials. Any other suggestions to try would be appreciated.

 

[cramer12]

Re: Trailer Lights

Another thought. When the trailer lights ground wire was disconnected, the trailer lights still worked. The left rear light works fine...it is only the right rear I'm having trouble with.

 

[Boatist]

Re: Trailer Lights

Cramer12 <br />What you just decribed is a classic bad ground wire for the light that is not working. Since the ground is bad when the light is on it will still light dim for the brake light if the clearance lights are off. It will actually feed back trun the clearance light and thru another clearance light to ground. <br /><br />Trust me, add a ground wire from ground in the light that does not work to a good solid ground on the frame or better yet back to the white wire and it will be fixed. I like to solder a ground wire right to the socket the bulb plugs into. Many light today do not have the old metal plugs where you can solder on a good ground.<br /><br />Personaly on my trailer I run a ground wire to every light. On saltwater trailers you would be suprised how many trailer sections do not make good grounds after a few years.

 

[Bass Runner]

Re: Trailer Lights

Ditto, it sounds like you lost ground on just the one light. Did you put in the adapter for the stock wiring harness on the tow truck or just splice into the harness?

 

[cramer12]

Re: Trailer Lights

I appreciarte your help. I'll see if I can figure out how to ground that light tonight and let you know what happens.

 

[cramer12]

Re: Trailer Lights

You were right. The light itself had a bad ground to the trailer. I had used the old semi-rusty washers which caused the problem the first time. (Remember, I told you wiring wasn't my thing.) So I sanded the trailer and used new washers and I was in business. Now I know what to do it I start having this problem again and can run a separate ground wire if needed. Thanks to all!