How To Repair an Ethernet Cable

Posted by on Oct 9, 2007 | 23 Comments

The broken connectorI’ve had a broken Category 5e Ethernet cable lying around for a while that I finally decided to fix. Actually, the cable was fine, but the spring on one of the modular connectors was broken, so it wouldn’t stay in a network jack. Since I’ve never done this before, I figured it’d be fun to document this little project. Stuff I used:

  • Package of RJ-45 CAT 5e Modular Connectors
  • RJ-45 Crimping Tool
  • Small Wire Clipper (optional)

Please read these directions thoroughly before cutting your cable.

(Trivial Side Note: Ethernet actually uses 8P8C connectors, but they are almost always referred to as RJ-45, technically a slightly different design. Details, details…) Step 1
Step 1: There are two wiring schemes for Ethernet cables, T568A and T568B. Both ends of the cable need to follow the same scheme. Since I’m only replacing one connector, I need to check which scheme the manufacturer used on this cable. This Wikipedia article shows the diagrams for both CAT 5e wiring schemes. Despite my color-challenged vision, I can tell by looking through the clear plastic that this cable uses the T568B layout.  (Of course, both ends of the cable need to use the same layout.) Step 2
Step 2: I lop off the defective connector using my RJ-45 Crimping Tool. This is pretty easy. There’s a nasty sharp wire cutter built into the tool. Step 3aStep 3b
Step 3: The crimping tool actually has a double blade which also scores the wire housing a half-inch from the cut end. This way, you can easily peel off the leader so that the exposed wires are the perfect length to insert into the new connector. However, I found that I needed some slack. After arranging the wires in the proper order, some were too short due to having been routed in a roundabout way. Perhaps, a seasoned wirer has a magic touch I don’t, but I opted to further expose an inch and a half of wire so that I could make my connection nice and pretty. For this, I used a small wire cutter to trim away more housing. (Nibble so you don’t stab your thumb like I almost did!) Step 4
Step 4: Now that I have plenty of wire exposed, I arrange them in the proper order. In this case, I’m using the T568B scheme. According to Wikipedia, this is from Pin 1 to Pin 8: White/Orange, Orange, White/Green, Blue, White/Blue, Green, White/Brown, and Brown.

EDIT: Keep in mind that there are two standard wirings for straight through cables, T568A and T568B — and crossover cables have different wirings at each end. Identify your cable wiring scheme first by looking at the wires through the transparent plugs at each end! (Your cable might not even follow one of these standards…) If in doubt, duplicate your existing wiring scheme.

Step 5


Step 5: I need these wires cut neatly so that they extend only a half inch from the cable housing. This way when I insert the wires into the modular connector, the cable housing will run flush into the end of the connector while the wires extend fully to the electrical contacts. I use a wire cutter to trim the excess wire so that only a half inch is exposed from the sheath. Step 6
Step 6: I orient the wires to the pin positions 1 through 8 of the new modular connector. It’s easy to do this upside down by accident, so I checked the pin positions on Wikipedia again just to be sure. Looking toward the head of the connector with the spring up, pin 1 is on the left side. I slide the wires in. Once they hit their respective grooves, they retain proper alignment all the way to the electrical contacts. Make sure to get them all the way in!Step 7
Step 7: Now I place the modular connector into the 8P jack of the crimping tool and give it a good squeeze. This locks down metal blades inside the connector onto each individual wire, thus establishing a circuit to each electrical contact on the plug. Crimping is my favorite step! Final Product That’s all there is to it. Now I’ve got a nice, clean, functional connector. It’s missing the snag-free collar of the original, but a lot of good that did me in the first place, huh? Only thing left to do is to make sure it works. Well, in order to do that, I plug the cable into my laptop and see if I can connect to the network. Voila!


Disclaimer: I have no idea if it is possible to fry your hardware if you mess up your pin outs, so proceed at your own risk! In fact, I’m not stopping you from purchasing an inexpensive cable tester to test your cables properly…so be smarter than me and do this instead of plugging it into your laptop.

That said, mine worked:

Final Product

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  1. Devin Columbus
    June 22, 2008

    Hey, thanks a lot for the guide. Just what I was looking for.

  2. prakash
    November 27, 2008

    Thanks for the simple but effective explanantion and pictures.
    Have a nice time

  3. mwhitt
    January 3, 2009

    Excellent explanation and pics documenting the process. This was exactly what I needed. Thanks!

  4. Alex Chapman
    January 7, 2009

    So helpful, I’m glad I found this. I have no experience with this type of thing and I was able to do it easily. This is the best explanation I’ve found, thanks!

  5. mysch
    February 22, 2009

    Thank you so much for these excellent instructions! I’ve never tried to fix these cables before but your directions have given me absolute confidence that it isn’t hard at all!


  6. Jono
    March 13, 2009

    Thank you! Now I can fight back against my cable loving cat…

  7. shreya
    April 1, 2009

    where did you buy the modular connectors? amazon is selling them in packages of 25 or 50, but of course that’s 24 or 49 too many…

    were you able to buy just a few?

  8. Kevin Danenberg
    April 1, 2009

    I bought mine at Radio Shack in a bulk package. I don’t remember how many. However, if you Google “RJ45 connector single” or “RJ45 connector 10-pack”, you should find a lot of options.

  9. Dave
    August 22, 2009

    Very thorough and informative. This is exactly what I was looking for. I really appreciate the link to the wiki that explains the different schemes as well.

    Bookmarked for future reference.


  10. Danny
    September 19, 2009

    Doesn’t the copper of the wires have to be exposed? if so how do I do that?


  11. Christopher Ivan P.
    September 20, 2009

    After having read your tutorial I did it a second time and I was successful.

    I actually did this yesterday and I failed only ONCE, Because I didn’t know that (on the first time) you’re not suppose to cut off the ends and expose the inside of the twisted pairs. But after reading your excellent instructions I was able to complete this project. I felt like a professional when I got my cable to start working again! haha

    the funny thing is, I did not originally have the tools for this project in hand. I had to go to the Electrical Supply store and the guy over the counter had told me that only Professionals can do it, Or people who have gone to school and trained for it.

    He even gave me a different color sequence to set up my order for the cables. Some Expert haha. Anyways.

    Good Tutorial. Simple and awesome.

    by the way …people should know…

    Crimping Tool – $14.99

    Pack of 10 replacement jacks – $3.00

    thats the cheapest I was able to find around my area :)

    Thanks a lot man.

  12. Kevin Danenberg
    September 20, 2009

    Great! I’m glad this tutorial is helping people.

    That’s correct — do not expose the copper of the wires or they will short against each other. When you crimp the modular jack with the tool, it will squeeze little blades inside the jack into each wire to make the necessary connections.

  13. Ahmed Abdel-Hadi
    August 23, 2010

    ThanX DuDe.. You Are a life saver

  14. Lauren Hutton
    November 4, 2010

    Great instruction for the male plug, but how do you pull up/straighten/align the contacts in female socket?

  15. Kevin Danenberg
    November 4, 2010

    Hmm… Sounds difficult. I’ve never had to do that. I guess if you can’t finesse the pins back into place, you’d have to replace the jack. That’s beyond me. I’d send it in for service.

  16. How to Repair Damaged Ethernet Cable Connectors | Marcus Emmanuel Barnes
    February 25, 2011

    [...] I recently set myself a small weekend project to repair some Ethernet cables I had with damaged cable harnesses (ends). I followed the directions provided by Kevin Danenberg on his blog post on how to repair ethernet cable. [...]

  17. Philmar
    August 5, 2011

    Hi. Thanks for the Info. Needed the refresher course, have done this before many years ago but could’n remember the parts name and tools required. Found all very cheap on amazon – even a cable tester for 4.00 dollars
    Oh the wonders of the internet – info first posted 2007 still useful and going strong.
    thanks again

  18. Al
    September 20, 2011

    Hi Kevin. I read this a couple of days ago and decided to buy a crimper and some connectors and after following your instructions I was able to get it to go on the first try. Thanks a lot man!

  19. Stephen
    January 30, 2012

    DO NOT follow his Wiki link for the layout. It is WRONG! I matched the layout I lined them up before I crimped the connector on, to the end I cut off, then double checked it on his Wiki link. It was “wrong” so I thought I had screwed up & cut it off. In redoing it again, I realize that I had it right the first time!….His Wiki link is WRONG WRONG WRONG!!!!!!

  20. Kevin Danenberg
    January 31, 2012

    Hi Stephen,

    I’m sorry you had trouble with your cable. The Wikipedia page correctly displays the T568A and T568B standards. Perhaps you had a crossover cable, which is different, or your cable followed some other wiring scheme? I’ve edited my post to hopefully be more clear. If you have a link to wiring that you believe is correct, please share.


  21. Benz T.
    March 19, 2013

    Hi Kevin,

    I’d like to send a big thank you for this guide that you wrote.

    Found broken spring on ethernet connector included with my brand new router. For some reason, no one in my area had ethernet cabling under 12-feet. I didn’t want 12-feet of cabling on my desk or wait a week to order a 1-foot cable from eBay, so I googled on how to repair Cat5e cables and your site was the first I looked at.

    Went to store, bought necessary crimping tool and connectors for around $15 dollars and followed your pictures and instructions religiously. I expected it would be difficult to get each wire into the right “channel” in the connectors, but once I sorted them in the right order and put them in the connector, they sort of slotted straight in.

    Had fixed cable with 10 mins thanks to your clear instructions and pictures. I double checked the wiring order on your site, and Wikipedia and also looking at old connector I cut off so I can confirm your T568B scheme is correct.

    Thank you again for your clear guide and saving me several days without internet!

  22. Kevin Danenberg
    March 19, 2013

    Glad to hear you solved your problem! Thanks for sharing!

  23. omika
    June 15, 2013

    thanks alot kevin. this is exactly what i want.

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