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Topic: Help me find the Ford 12v trailer line (Read 298 times) previous topic - next topic
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Help me find the Ford 12v trailer line
I'm trying to find the 12v line that Ford (2003 MB) provides for providing 12v power to a toad or trailer.

I started here: 7pin trailer connector

and was able to find the 2 wire connections (black and brown) that contain the typical 4 way trailer connections and the extra 3 that make up 7.   On my mid-bath, those are located between the fuel tank and the gray water tank.   I can see and touch them, but they aren't easy to reach.

The 7 wires from those pigtails enter a wire loom and I traced that loom to the rear of the coach where only 4 wires emerge.  

My question is - before I go tearing into the neatly packaged and hard to reach wire loom, does anyone know where the 3 extra wires should end.   Do they go a few inches into the loom and ends (ie. look for them close to the black and brown pigtails) or do they extend some distance towards the rear of the coach (look for them closer to the bumper)?

Can anyone who has anyone found this 12v wire give me some tips?

Rich

2003 MB
Re: Help me find the Ford 12v trailer line
Reply #2 –
Rich-

I realize you know most of what's below. I'm providing a fuller explanation for anyone coming along later.

There are two Ford connectors at the rear. LD used one (on your model year). The unused one contains the wire that you want.

Follow the wires forward from the bumper. They will follow the inside of the driver's-side chassis frame. Just in front of the grey water tank, and in back of the gas tank you'll find the two connectors. The one you want has three wires. LD should have installed the Ford-supplied pigtail in that connector.

Carefully unwrap the tape that's on the bumper-side of the connector. The pigtail should emerge. It will have about 8 to 12 inches of wire on that end. The trailer charge line is one of them (I'll have to look up the color code). Use a weather-resistant butt splice connector to attach your 10 or 12 AWG charge line extension wire to the pigtail. If you plan to use the other wire(s) in that connector, extend them at the same time. Then, apply new tape to the pigtail and tuck it back up in its cubby, where you found it.

Note: Before you attach to any wire remove it's fuse first. that way you ensure you won't accidentally short out the wiring upstream of the connector.

I replaced the LD's 4-pin connector with a 7-pin, and brought all 7 signals from those two connectors to the 7-pin hitch connector.

Note: If you can, avoid disconnecting the connector halves. The plastic will have become brittle, and there is a real chance you will break one or both halves. When I rewired I had purchased replacement pigtails and wired them to their extension cables in advance. Using new pigtails eliminated splicing under the coach. I was fairly confident I could separate the connectors without breaking them, and I did. It could've gone south, though.

Note: Starting with the 2004 model year chassis, Ford separated the chassis and trailer wires onto different connectors. I forget if it was (the original) two for the chassis and the new one for the trailer, or vice-versa. It's not too hard to look that up.

Mark H.
Former owner, 31-foot gas Class A
Former owner, 1997-8 mid-bath
Re: Help me find the Ford 12v trailer line
Reply #3 –
Rich,

For our ‘15 LD the Owners Manual has a line art image of the plug in question. Here it is as an attachment.

Kent
2015 27' RB "MissB.Haven"
 
Re: Help me find the Ford 12v trailer line
Reply #4 –

To follow up on this:

I found the orange switched 12v line and was able to get a wire onto it.

On my MB, you can see the 2 black and brown wire wire connectors by looking up between the fuel tank and the gray water tank.   From there, the wires travel back over the gray tank inside some wire loom.   As suggested by Mark above, it's a matter of unraveling the electrical tape / wire loom / more electrical tape that the wires are running in until you find the wire(s) you're looking for. 

 I came at it from behind the gray tank; there is space to work with a light and a knife and pliers above the tank.   I removed (and later replaced) one of the 1/4" hex head screws to loosen the P-style cable clips and create some slack.  You can see a wider spot in the wire loom, which is where the 4 wires from the brown harness are spliced to the wires running to the back of the coach.   This is also where the 3 unused wires end.    Once you get the 3 wires from the Black harness exposed, they are just cut flush and waiting for someone to put them to use.    Orange is the 12v switched line that I was looking for.

Now I have a 6-pin connector with the traditional flat-4 wires [Green (Rt/Stop), Yellow (Lt/Stop), Brown (tail/side), White (Ground)] and the 5th 12v wire.    I put a Towed Battery Maintainer in line on the 12v wire, so I can switch between toads (I have 2) without having to wire each individual vehicle.  

This is what I used:    Amazon.com: Briidea Towed Vehicle Battery Maintainer, Easy Installation :...

Rich
 

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2003 MB