Trailer Connection
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Senior User
Joined: Aug 2011
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From: NC
Trailer Connection
I was getting ready to tow a TT before I committed to saying I would tow I was checking my plug, usually on the 7 plug, you'd have a 12V constant and then of course trailer brakes, lighting and such. My 12V constant was showing 0.0, so I checked everything else and with lights off 0.0, but with lights on around 12V. Most of the trailers I will be towing will need the 12V constant. I have checked the fuse panel pertaining to trailer connections and all the fuses are good, I still need to keep the lid open and test the turn signals and all. Before I have Ford waste $60 figuring it out I would like to steer away from them if need be. What should I try to so I can finally get stuff back on the road and such?
I'm hitting easy street
Joined: Nov 2009
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From: Central Oregon
You might want to post in this area also. Lots of knowledge on towing and trailers.
Towing, Trailers & 5th Wheels - Ford Truck Enthusiasts Forums
Towing, Trailers & 5th Wheels - Ford Truck Enthusiasts Forums
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Senior User
Joined: Aug 2011
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From: NC
I tried it both with these ways
engine off - no voltage
engine on - no voltage
I have to get some alligator clips so that I can confirm running lights, turning signals, reverse and brake controller
engine off - no voltage
engine on - no voltage
I have to get some alligator clips so that I can confirm running lights, turning signals, reverse and brake controller
New User
Joined: Aug 2011
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From: Morrison
Well i had the same problem but i had a bad ground and all i did was i got out a ginder and ground down the spot i wanted to put my ground wire and the i didnt have any problems.. but i did have to put my running lights connected to my licence plate wiring
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Senior User
Joined: Aug 2011
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From: NC
I have checked ground on both the 7 and 4 connection, they are good, I am planning on going to a trailer shop that I trust and see if they can figure it out, I have worked with them before. Most likely the person who had the truck before me accidently snipped one of the wires.
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On a 2004,
#6, Trailer Turn/Stop lights
#38, Trailer Park lights
#39, Trailer Backup lights
#101, Trailer Brake Controller power
#115, Trailer Battery Charge (this is the 12V feed one)
Make sure you test the fuses, don't rely on a visual inspection. You can use a test light and test the in place by probing where the blade is exposed on the back of the fuse. Or you can take the fuse out and use a continuity meter.
Relay #305 is the Trailer Battery Charge Relay.
You can use a standard test light to test the plug, hook the alligator clip to the ground pin then test the other pins. The diagram is on the plug cover. Or you can see a diagram here.
Trailer Wiring Diagrams | etrailer.com
#6, Trailer Turn/Stop lights
#38, Trailer Park lights
#39, Trailer Backup lights
#101, Trailer Brake Controller power
#115, Trailer Battery Charge (this is the 12V feed one)
Make sure you test the fuses, don't rely on a visual inspection. You can use a test light and test the in place by probing where the blade is exposed on the back of the fuse. Or you can take the fuse out and use a continuity meter.
Relay #305 is the Trailer Battery Charge Relay.
You can use a standard test light to test the plug, hook the alligator clip to the ground pin then test the other pins. The diagram is on the plug cover. Or you can see a diagram here.
Trailer Wiring Diagrams | etrailer.com
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Senior User
Joined: Aug 2011
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From: NC
I'll check tomorrow and if my job needs me to tow something this week I'll tell them to write me a check to get new fuses. Hopefully it's just probably fuse 115, cause 5,38,39, and 101 are good, I must of missed the 115 fuse by mistake, I think I was outside in the heat trying to figure it out.
Elder User
Joined: Jul 2009
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From: Smiths Grove, KY
Also check out the following link which shows the truck electrical diagram for the fuses and relays listed by above by dchamberlain.
https://www.fleet.ford.com/truckbbas...bb_pdf/189.pdf
https://www.fleet.ford.com/truckbbas...bb_pdf/189.pdf
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