I have a 2004 F350 with the v10 and I'm not geting the left / right or stop lights to work throught the trailer plug I checked all the fuses and messed with the relays under the hood (not sure what I'm doing just looking) I do have tail light at the plug. Can't see anything wrong with the wire harness. anyone have any Ideas? (Go gentle this is my first time)

 

Welcome to the site..

We're all about gentle here

First, if you have a 12v test light? make sure you have 'voltage' at both sides of fuse F2.6 20amp in the central junction box.. Not just checked for an open/blown fuse.. If you have 12v on both legs of the fuse, remove one of the trailer turn relays in Aux box 4 (small box closest to the inner fender drivers side) and check for voltages there.. Here's a quick diagram of the relay connector..

If the fuse is good, you should have 'battery voltage' on terminal #3 in the relay box (R&L relays) with the relay/s pulled.. And with R or L direction selected and depending on which relay you removed, you'll have 'flash' function on terminal #1.. You can 'bridge' the relay connections #3 and #5 and the trailer connector lights should be steady ON which will take the multifunction switch out of the diagnostic.. If the relay connection is bridged and you still have no lamp function, it's between the relay box and the trailer adapter, or possibly a bad ground at the rear connection.. The main trailering harness plugs into the back of the plastic 7 way connector and could possibly be there, but usually not for mutiple circuit problems....

 

I do have a 12v test lamp and I have power on both sides of the fuse (I assuming you ment with the fuse in) then I went to the R&L terminal #3 and I don't have any power

 

Was there a 'flashing' input when checked with your test light to either of the trailer relays on the #1 terminal (R/L direction dependant) shown in the diagram? Chances of it loosing both power distribution circuits, one from the multifunction switch to cycle the relays on/off, and the other from the central junction box for the load distribution would be a little unlikely.. If I remember correctly, we had a very similair issue in the past with an SD that had a bad/corroded (?) wire under the #4 relay box that the insulation had split/buldged and came apart.. Might have a look under the relay box, and if it looks OK, (and you have a 'flash' input from the multi function circuit) try using a test lead and add 12v to the DG/OG wire to see if both trailer lamps come on line and function..

 

Yes I do have a flashing input on the #1 terminal. I'm sorry I should have told you that last time. I'm not sure what you mean buy DG/OG you'll have to dummy it up for me. I looked at the wires and form what I can see they look good tryed to take the cover off the bottom but did'nt want to break it.

 

Ok I just went out and got the cover off the bottom and all wires look good I then jumped from the #1 terminal to the #5 terminal and had flashing power at the plug in back Now what does that mean

 

By bridging the 1-5 you completed a circuit from the multifunction/turn switch 'output' that is supposed to supply 12v to the relays 'magnetic coil' to cycle/close the trailer lamp relay contacts, and instead, fed it direct to the trailer lamp connector/adapter circuit.. But, the relay is in place to control the lamp load for the trailering lights with the mutifunction switch in control of the trailer relay coil on #1 terminal..

Where does that leave you

It means that there's no connection issues from the relay back to the trailer adapter! and that the mutifunction switch is adding a pulsed voltage on the #1 terminal as it should.. So, if you take a test lead or long wire and add 12v to the 'Dark Green/Orange' wire and the lamps/relays function as they should, then there's an 'open' in the power distribution from the power distribution box out to the relay box #4..

 

Ok I will try that and get back to you with results. thank you for all the help so far

 

Ok I jumped 12v power to the DG/OR and then tested at the plug and had a flashing light so do'es that mean I have a bad wire from the main fuse box out to the relay? and if so do you know what where or how to trace it down? the only thing I can think of doinig is to pull all that wire out of the loom and poke and hope

 

I found the problem. Thanks for all the help from “Hayapower”. It was a corroded wire on the fender well. After I was told what wire to look for (the dark green with the orange stripe), I traced it from the main fuse box under the dash out to the plug on the fender, testing for power at each connection. The dead giveaway was that I noticed some green powder on the outside of the wires going to that plug, so I started pulling them apart until I saw the DG/OG wire and found where it was bad. I have some pics of the wire stripped and ready for repairs. I hope this will help someone else and save them some time. I spent three nights looking for this. The last pic is my helper taking it for a test run