Due to a bit of age/corrosion, I have decided to replace the 7 pin plug/cable on the trailer.As I usually do when I am about to tackle something I haven't previously dealt with, I searched the net and YouTube for tutorials/instructions just to make sure I don't miss anything.The funny thing was, out of all the vids/articles I reviewed, only one could be found that touched on replacing the entire cable (ie wiring directly into the junction box).Every other one described how to either replace the plug (by cutting the old plug off) or cutting/splicing the cable farther up. In fact, in one video, the fellow showed the old cable, and existing junction box, then proceeded to cut the old cable halfway, and splice in a few feet of the new cable and plug using another junction box to connect the new and old cables, then fastening the new junction box right next to the existing junction box (with the old cable running from one box to the other).To me it seems simpler to remove the entire old cable, get a new cable and run it right to the existing junction box. Or am I missing something??Marv

Maybe the new cable was too short for his application. More contacts and breaks, more corrosion possibilities and breakdowns. I would go with one junction box.

I managed to pinch my cord between the hitch and king pin. Bought a new one at a local trailer shop and installed it myself. They had different lengths available. Really pretty simple. Open the junction box and look closely at the existing wires. Maybe even tag and/ or take a picture of them to make sure you get them back correctly as you may have some where two or three wires connect together to the new cord. That way there will be no second guessing about what goes where. But again, nothing to really worry about.

Fisherman wrote:Maybe the new cable was too short for his application. More contacts and breaks, more corrosion possibilities and breakdowns. I would go with one junction box.X2!Most likely the person in the video was not able to get a cable long enough so splicing somewhere else would be needed. Not ideal but could work in a pinch.As someone else mentioned, they do sell prewired/molded cables with plugs in different lengths and even different wire ga sizes. You can also buy bulk wire for 7 pin harness to customize your cable to the length you need and then add a replacement plug to that.Much better however to get a cable long enough or even a bit longer in the first place and go back into the original junction block. Otherwise you are adding an additional point of failure with an additional splice. Extra junctions or splices can eventually come back to bite you in the behind and that typically happens at the worst possible time..

I would use crimp butt splicers and Heat Shrink insulation tubbing.

Dusty R wrote:I would use crimp butt splicers and Heat Shrink insulation tubbing.:RRookie mistake.Crimps work best with proper quality crimping tool, very few people have the proper crimping tool and substitute pliers and crush the connection making a very poor and unreliable connection.Additionally, standard heatshrink tubing is not weather proof or water tight and moisture will destroy the connections hidden inside the tubing.Not to mention the average backyard electrician won't have a good heat gun and will use matches or a lighter to shrink the tubing making a mess of the job..For heatshrink tubing to work in the outdoors you must get adheasive lined tubing, it has a heat activated glue that surrounds and seals around the wire insulation making a good water and weather tight seal..But, a good electrician will try to avoid allowing connections to be exposed to weather which means taking the connections back to the original connection box which is protected from the weather.Inside that box, the connections are made with wire nuts, no need to reinvent the wheel. Just use the existing wire nuts inside that box and all will be fine.

7 pin cable | Good Sam Community

16 Replies

marpel
Explorer
May 26, 2022
Thanks for all the replies:

Just to clarify though, the new cable was not too short as the new box was placed right beside the old box, so the, loosely strung, replacement cable appeared able to reach the old box quite easily.

And BB_TX, your description was exactly what I was planning on doing. Take photos or label current box layout and just repeat with new cable. Logically seemed pretty straightforward.

Just figured, because no-one seemed to want to tackle the junction box connection in any of the vids/tutes, that I was missing something that made it difficult.

Marv
Gdetrailer
Explorer III
May 26, 2022
Dusty R wrote:
I would use crimp butt splicers and Heat Shrink insulation tubbing.

:R

Rookie mistake.

Crimps work best with proper quality crimping tool, very few people have the proper crimping tool and substitute pliers and crush the connection making a very poor and unreliable connection.

Additionally, standard heatshrink tubing is not weather proof or water tight and moisture will destroy the connections hidden inside the tubing.

Not to mention the average backyard electrician won't have a good heat gun and will use matches or a lighter to shrink the tubing making a mess of the job..

For heatshrink tubing to work in the outdoors you must get adheasive lined tubing, it has a heat activated glue that surrounds and seals around the wire insulation making a good water and weather tight seal..

But, a good electrician will try to avoid allowing connections to be exposed to weather which means taking the connections back to the original connection box which is protected from the weather.

Inside that box, the connections are made with wire nuts, no need to reinvent the wheel. Just use the existing wire nuts inside that box and all will be fine.
Dusty_R
Explorer
May 26, 2022
I would use crimp butt splicers and Heat Shrink insulation tubbing.
Gdetrailer
Explorer III
May 26, 2022
Fisherman wrote:
Maybe the new cable was too short for his application. More contacts and breaks, more corrosion possibilities and breakdowns. I would go with one junction box.

X2!

Most likely the person in the video was not able to get a cable long enough so splicing somewhere else would be needed.

Not ideal but could work in a pinch.

As someone else mentioned, they do sell prewired/molded cables with plugs in different lengths and even different wire ga sizes. You can also buy bulk wire for 7 pin harness to customize your cable to the length you need and then add a replacement plug to that.

Much better however to get a cable long enough or even a bit longer in the first place and go back into the original junction block. Otherwise you are adding an additional point of failure with an additional splice.

Extra junctions or splices can eventually come back to bite you in the behind and that typically happens at the worst possible time..
BB_TX
Nomad
May 25, 2022
I managed to pinch my cord between the hitch and king pin. Bought a new one at a local trailer shop and installed it myself. They had different lengths available. Really pretty simple. Open the junction box and look closely at the existing wires. Maybe even tag and/ or take a picture of them to make sure you get them back correctly as you may have some where two or three wires connect together to the new cord. That way there will be no second guessing about what goes where. But again, nothing to really worry about.
Fisherman
Explorer
May 25, 2022
Maybe the new cable was too short for his application. More contacts and breaks, more corrosion possibilities and breakdowns. I would go with one junction box.

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7 pin cable

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