Trailer running lights

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  #1  
Old 09-16-10, 07:20 PM
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Trailer running lights

I borrowed the Company 2006 Ford F150 for a night trip and my pre trip check found I had no trailer running lights with the truck lights in full bloom. I checked both trailer bulbs and they looked good. Both the right and left hand turn flashers and emergency flashers, and brake lights will illuminate the bulbs but not just the headlights on. I checked the trailer plug for a hot 12 volt line that wasnt hitting intermittently like the turn signal and flashers were and found none. I have found fuse locations in the owner manual for every operation described above, but not one for just the running lights...what am I missing here?
 

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Old 09-16-10, 07:25 PM
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Most trailer issues are from a poor connection between the truck and trailer. Remove wiring plugs and clean the "prongs" on both the truck and trailer with emery cloth or sandpaper. A lot of times just a wiggle of the plug will get the lights working but may not be very long. That is why I recommend cleaning the connections.
 
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Old 09-16-10, 07:48 PM
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Trailer lights

I have good clean connections. What I don't have is a straight 12 volts to one of them for the trailer running lights to stay on. I know I have a blown fuse or relay but there is none identified in the owners manual except a 10 amp in position 14 listed as a backup lamps and daytime running lamps relay coil. I will check this tomorrow when the light is better...
 
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Old 09-16-10, 07:52 PM
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There can be all sorts of problems with this. Many times things are not wired properly.

And with trucks, there can be factory wiring which should be done right, but there can be fuses and relays under the hood for trailer stuff. These might only go to the trailer wiring.

And with trailers, no telling how the wiring was done. Can be a ground problem where the hitch is the only ground connection (not good). Or sometimes there are electronic gizmos on trailers which convert 3 wires to 2 wires or whatever. Here is what one of those looks like...
http://dr650.zenseeker.net/SignalLig...tConverter.jpg

I would start with the trailer electrical connector and a multimeter. See if the problem is with the truck or with the trailer.

Trailer wiring...
Trailer Wiring Diagrams | etrailer.com

Another way to do this is to connect the trailer to another vehicle (known working connector) and see if it works as it should.

Or to connect another trailer to the truck and see if that works OK.

P.S. And for your added pleasure, someone decided to make the truck end wire colors different from the trailer wire colors! Beware of that!
 
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Old 09-16-10, 09:43 PM
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The last time I went to get my trailer inspected, I believe the guy had me turn on the 4 ways, and one turn signal. If everything flashes, there is a bad ground.
 
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Old 09-17-10, 03:13 AM
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I believe the 06 F-150 has another small fuse panel under the hood if this is factory wiring.. I think it's to the rear (or maybe to the left) of the Power Distrubution box under the hood.. It's along the outside of it, I remember that & the trailer fuses are in it.. It's only a small one & kinda outta sight. Look close & you'll find it if I remember correct...
Roger
 
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Old 09-17-10, 05:31 AM
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No Trailer running lights

I found the small fuse box under the hood, and both fuses there were ok, (don't know about the relay or testing them)

For everybody else this is all factory wiring and the problem is in the truck, trailer lights work with twelve volts from another source.
 
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Old 09-17-10, 09:19 AM
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I suppose since you borrowed the truck, you could run a 12 volt line from the cigarette lighter (or whatever) to the lights.

If you wire anything directly to the battery, be sure to use a fuse.

Some trailer connectors have a constant 12 volt power on them. You could maybe use that as well.

As to the truck, if there is a second battery, these are typically used for trailer power. Maybe the second battery is missing or dead or a fuse to it blown?

Other than that, your pretty much going to need a factory wiring diagram to see how the circuit works, what all is on the circuit, what wire is what, etc. That would come with a factory service manual set of books which you can order from the dealer or helminc.com. But these can cost $150 for the set, so I would not be buying that for a borrowed truck...
 
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Old 09-17-10, 06:45 PM
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No Trailer running lights

I like challenges, but I don't need this one right now. Maybe Ill drive a RAM for 60 days....

Thanks for the reply!!!
 
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