runnig.tail light trailer wont work rest work fine (brakelight,right,left light)

[Tim1]

I have question about trailer running/tail light , somehow i cant understand how it works, I have trailer brakes,left right and brake light working but running/tail light have no power to it at rear trailer plug. i checked all the fuses and they are all good. where is the trailer light from plug go intro to I tried to follow the wire but I cant find it ? and does it have fuse ? (i checked also all fuses on the hood and they are all good as well )
my truck light are working fine. thanks a lot for your help

 

[siegler]

What truck do you have?
Do you get 12 volts to your trailer plug (assuming your dealing with 6 or 7 pin wiring)

I just went through the same thing. Ended up being a fusable link next to the passenger side battery (on a 90 or 91 truck, may be different on other years)

 

[franklin2]

Year of truck is important, along with are you using the factory tow harness or is it spliced into the factory truck rear light wiring for the trailer?

 

[OLDBULL8]

On a 7 pin receptacle it's the Brown wire for running lights.

 

[Tim1]

Thanks a lot for all your help, mine truck is 7.3 turbo 1994 single cab xt longbox. yes I deal with 6 plug and brown/white line cable doesn't have 12 volt, its super hard to track down that cable all the way to the front so where is that cable go intro to ?

 

[Tim1]

What truck do you have?
Do you get 12 volts to your trailer plug (assuming your dealing with 6 or 7 pin wiring)

I just went through the same thing. Ended up being a fusable link next to the passenger side battery (on a 90 or 91 truck, may be different on other years)

where is this fuse located ? I dont see anything thanks

 

[DaveBen]

Tim1, please fill out your signature, by going to the SETTINGS at the very top, right hand side of the HOME page. Add your truck and where you live, in general. This will help all of us.

 

[siegler]

where is this fuse located ? I dont see anything thanks

Your 1994 doesn't use fusable links like earlier trucks. Fuse D in the fuse box in the engine compartment is for your marker lights. The relay for the marker lights is also in that box, that could be bad too.

 

[Tim1]

I checked all the fuses there and they all in good shape, how do you test relay, what do you mean by markers light ? thanks a lot

 

[siegler]

I checked all the fuses there and they all in good shape, how do you test relay, what do you mean by markers light ? thanks a lot

If the fuse is good, you get 12 volts to the relay socket, but no 12 volts to the trailer plug when the running lights for the truck are on, I would be tempted to just replace the relay. I think they are pretty cheap.

 

[direwulf23]

Check your light switch for burned terminals

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[Tim1]

If the fuse is good, you get 12 volts to the relay socket, but no 12 volts to the trailer plug when the running lights for the truck are on, I would be tempted to just replace the relay. I think they are pretty cheap.

which relay is it ? thanks

 

[Tim1]

Check your light switch for burned terminals

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you mean the one inside the cab ? so I have to take plastic behind steering off and then look behind there ? or do you mean other kind of switch ? thanks

 

[direwulf23]

you mean the one inside the cab ? so I have to take plastic behind steering off and then look behind there ? or do you mean other kind of switch ? thanks

In the cab, yes. The actual light switch that you use to turn your headlights/ running lights on.

 

[siegler]

which relay is it ? thanks

Unfortunately, I'm unsure which one is which in the box, I haven't been inside of a 1992+ engine compartment fuse box. I have only been going off the wiring diagrams.....

The middle relay is the horn relay, the trailer marker light relay and the fuel pump relay are on either side of the horn relay. This is by looking at the diagram, not the actual box....