Cat5e cable run in the wall isn't working

Posted on 2016-07-30
Last Modified: 2016-09-02
I came across an existing run that is probably 100 ft or more.  I used a Toner Wire Tracker to mark the cable inside of the networking utility cabinet.

I then proceeded to first plug one end into a switch and the other end into a router.  No green lights.  I tried it directly into a computer and switch.  No green lights.

I grabbed my S1007 network cable tester and it only displayed "4&5" as green.  I recrimped both ends using T-568B and tried again, still only 4&5 as green.  I then made one end T-568A and tested again, and still 4&5 as green.

I'm stumped.  I've recrimped both ends several times and the only thing I get is 4&5 green on the S1007 network cable tester.  I tested the tester with a known working run and it cycles through the 1&2, 3&6, 4&5, 7&8 cycle.

Any suggestions?
Question by:tigermessage
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Assisted Solution

by:Dave Baldwin
Dave Baldwin earned 100 total points (awarded by participants)
ID: 41736052
Sounds like one or more of the wires are broken or cut.  If you have a loop-back plug, you can check for continuity.
LVL 92

Assisted Solution

by:John Hurst
John Hurst earned 100 total points (awarded by participants)
ID: 41736055
Internal wires could be broken as per above or the cable could be linked. (cross wired) or stretched .

You will probably have to rewrite or provide an alternate path
LVL 92

Expert Comment

by:John Hurst
ID: 41736062
Also remember that any deformity (kink, stretch) can affect the twisting and so the inter-conductor capacitance. This affects the range and performance of the cable.

Expert Comment

ID: 41736099
One thing extremely odd about your setup is that cable run going inside a network utility cabinet should use solid wire.
You should preferably not use connectors on them, use female RJ-45 connectors or patch-pannels.

Patch cable are more supple (they use stranded wire) and normal connectors are designed for them.

Using connectors for stranded wire on solid wire is a receipt for problems

Short-circuit all cables on one side then use ohm-meter on the other side.
That will at least tell you if a cable is broken (it's likely), or if you are using the wrong connector.
LVL 78

Accepted Solution

David Johnson, CD, MVP earned 100 total points (awarded by participants)
ID: 41736139
does your network tester also have a reflectometer to measure distance? Some can tell you where the break is.
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LVL 24

Assisted Solution

by:Dr. Klahn
Dr. Klahn earned 100 total points (awarded by participants)
ID: 41736146
If you don't have a TDR to check the pairs, try this:

Cut the connectors off.   Short each pair of wires by individual pair at one end.  At the other end, use a DVM to check continuity across pairs.  If one of the wires has been cut, there will be no continuity between (at least) one pair.

After checking continuity of each pair, see if you have two good pairs left.  If so, you may be able to salvage the cable if only the first two pairs are in use.  (This is the common situation.)

If not using all four pairs, re-punch new connectors on pins 1,2,3,6 using the two good pairs.  Then re-check the cable with the network cable tests.  Pairs 1 and 2 should show good, pairs 3 and 4 disconnected.  Tag the cable at both ends "SEVERED WIRES, NON-STANDARD PUNCH" so that the next tech who sees it won't think it's a good cable.
LVL 92

Expert Comment

by:John Hurst
ID: 41736149
Remember what I said above:  If the cable is damaged and the inter conductor capacitance is affected, that will not show up in ohmmeter conductor tests.
LVL 20

Assisted Solution

CompProbSolv earned 100 total points (awarded by participants)
ID: 41736226
The suggestions about shorting one end and testing the other with an ohmmeter will tell you if there is a break in the cable.  I find that to be pretty rare (that is, some wires broken and others fine) but not at all impossible.  Imagine if a rodent has been chewing on the cable!

John is correct that capacitance problems (as well as many others) won't show up in a continuity test but will keep the cable from working properly as an Ethernet cable.  The key here is that your tester is just doing continuity tests so the failure of several pairs says that there's a pretty basic problem with the cable.  The capacitance problem would show up when the cable passes the continuity test but won't work for networking.

Expert Comment

by:nader alkahtani
ID: 41736255
You should replace the cable , it may broken , but for more troubleshooting :
I would use the great Cisco command test for (TDR Time-Domaine Reflectometer)
 cable-diantgnostics tdr interface <interface>
followed by :
show cable-diagnostics tdr interface <interface>
it will show you the distance to the broken area of cable

Expert Comment

by:nader alkahtani
ID: 41755387
Dear!  Is it resolved?
LVL 24

Expert Comment

by:Dr. Klahn
ID: 41781293
All useful approaches, but no closing commentary from questioner.

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