I have pulled wires in my apartment and was terminating them to RJ45 for computer usage as well as extensions for USB and control signals.
From experience here are the things that I know Murphy could do prior to today:
1) All the wires are not pushed in enough into the connector, resulting in no connectivity on that pin. Start over and ensure the cables have an even length when arranged in the right order.
2) One or multiple wires didn't get the right position. Make sure to check the wires properly before punching them down. Just try again until you get it right, it might help to strip a bit extra of the wires and then cut the excess once the order has been arranged.
3) One or multiple pins is not pushed down properly. Try to crimp it again and if that doesn't help it's time to get a new crimp tool.
4) Cutting through the inner wires while removing the shielding. This is easily done, and I would require anyone to redo a cable if the inner core of any wire can be seen. Having damaged wires could lead to intermittent faults which you don't want to risk!
5) Placing the cables the wrong way around. Easily done if you stick the cable on the opposite way from what you are used to. If not a critical cable you might get away with doing the same on the other side since the pairs are still intact but preferably the cable should be redone.
6) Mixing EIA-568-A and EIA-568-B. For resons which I don't know there are two standards for how the pairs should be connected, EIA-568-A and EIA-568-B. For some reason USA only recognize the A standard resulting in patch panels and other equipment to only be marked with the A standard sometimes. The B standard is supposed to be an improvement and is recommended in Europe. The important thing is to follow the same standard on both end of the cable, if in doubt I would suggest EIA-568-A since that's supported by everyone. If the standards get twisted, just redo one side to correspond to the other.
As you understand the connectors do go wrong sometimes. But if you are careful and inspect the connector properly before terminating it most of the problems can easily be avoided.
So when I terminated the wires at home I did as I always have done and ensured the wires was in the right order roughly the same length and that I managed to push them all the way into the connector. After I finished all of the wires and started testing them I found out that I had a short on the first cable. I thought I had been quite gently when I pulled the wires and started to trace the cause of the problem. Using a standard multimeter I could see that the fault must be in or near the connector because of the minimal resistance to the fault.
I cut of the connector to validate that the problem was on the connector end. I continued to strip of the shielding from the cable completely to ensure I hadn't damaged the inner cores. Everything looked fine, I then cut the connector in pieces to ensure that the cables wasn't touching each other. I _STILL_ had the short on the cables, I could not believe it! I checked and double checked and finally I found the cause. The tubes that the wires are pushed in to ensure they get to the right location didn't go all the way to the end of the connector, at the very front of the connector the conductor of the stranded cables that I had used had been pushed towards the front wall and made a connection with the neighboring wire.
After finding the problem on the first wire I checked all my connections and all of them had at least two wires short circuited one of them had 4 out of 8 shorted but non of the cables that I done with the Cat5e cable was without a fault.
So I can now add a 7th possible problem when terminating RJ45 connectors, pushing in the cable to far. The fact is that even after knowing of the problem I could still not ensure a proper termination.
7) Short circuit by pushing in the wires to far into the jack. Solution: get other jacks! The plugs
This whole story has convinced me to start using Platinum tools EZ-RJ45 (http://www.platinumtools.com/index.html) connectors istead. The wires are pulled through the connector and their crimp tool then cut of the excess, should be both quicker and more secure and most important Murphy can try to put a number 7 on me then!
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