New Cat 5 wire, tests OK but doesn't work.

bobslay · Mar 25, 2013

Hi, I've just installed a new run of cat 5 cabling as the old one ran partly outside and it just gave up after 3 years of harsh winters. The cable runs about 30m from my PC to my router. I put RJ45 plugs on each end myself and I have a simple tester to test it out with the 8 consecutive lights.

The tester shows the cable is working fine but when I connect my PC to my router with it I get no connection at all, I'm clueless.

The cat5 cable was quite cheap but I thought if the cable tester said it was OK then it should work.

Any thoughts?

Thanks

atomicWAR · Mar 25, 2013

is it possible your old cable didn't go bad and rather your router port or your PC nic did instead?

bobslay · Mar 25, 2013

I've been running a temporary cable through the rooms of my house (rather than through the ceiling where the new and old one run) since it stopped working, that cable is working fine so it must be the new cable. Is there any way it the tester says it's OK it could still be bad?

atomicWAR · Mar 25, 2013

it's possible...even likely the tester is wrong if one cable works and another does not. one thought though....does the cable pass close to any electrical lines or something with a serious magnetic field. if so current could be induced on the wire screwing up the signal.

bobslay · Mar 25, 2013

Tester could be wrong but tester identified old cable wasn't working and the temporary one was. The route of the cable hasn't changed for three years so any magnetic/electrical interference would have been around all the time and I've been running fine at 110Mb.

If the new cable is poor quality compared to the the one it's replacing could it now be showing interference whereas before it wasn't?

Jim_L9 · Mar 25, 2013

Does your link light on the router light up when you plug in the cable? Is there a link light on your PC, if so it should also light up.

bobslay · Mar 25, 2013

No lights on either the PC or the router

atomicWAR · Mar 25, 2013

bobslay :

absolutely....cheap wires tend to have poor shielding. also, did you try the wire before you ran it through the roof? or conversely pull it out and try it like your temp cable is by running through the rooms.

bobslay · Mar 25, 2013

Sorry just to clarify there are lights but they are not lighting up with the new cable (they used to light up on the old one and they light up with the temporary one)

atomicWAR · Mar 25, 2013

bobslay :

yeah then its a bum cable....sorry. i use to be in the navy and have to run cat 5 cable all over ship so i know what a pain in the back side redoing that is. wish the news was better.

bobslay · Mar 25, 2013

@AtomicWar
Stupidly I didn't test the cable before running it, I was too excited

Difficult to pull out to test.

bobslay · Mar 25, 2013

OK thanks, time to get the ladders out again and stop being so tight on the quality of the cable. Still seems very strange to me that the cable tester is saying it's fine but I guess that means it's getting a signal but not a great one.

atomicWAR · Mar 25, 2013

bobslay :

been there done that...and yeah its probably getting signal like you said just not a good enough one...

Jim_L9 · Mar 25, 2013

Most cabling problems I have had with the self made cable are bad terminations. I would cut off one end and crimp a new end and then try the other. How do they look visually? Did you make sure that pins 1 and 2 are a twisted pair and also make sure pins 3 and 6 are a twisted pair?

bobslay · Mar 25, 2013

Thanks, new super turbo shielded bomb proof cable ordered, thanks for your help. From the excitement of seeing the 8 lights all come on to the disappointment of no network, it's been an emotional morning

bill001g · Mar 25, 2013

Note if you have a very simple cable tester that just shows continuity but does not actually test the pairs you could have a cable that tests good that is wired wrong. If you have the pairs wrong it will not work. A very common mistake is to wire it 1,2 3,4 5,6 7,8 when you must wire it 1,2 3,6 4,5 7,8.

molletts · Mar 25, 2013

bobslay :

It could be that one (or more) of the connections is good enough that the tester thinks it's OK but not quite good enough to get a clean signal through. I've had this once or twice before, when I've had to crimp RJ45 plugs onto solid-core cable that's used for structured wiring as opposed to the stranded-core cable that is normally used in patch leads (you can actually buy special RJ45 plugs for this use which make it a lot easier and more reliable but normally, you'd fit a socket to each end instead).

Have you tried giving the crimp tool another good squeeze on each end of the cable, just to make sure the crimps are really well done?

bobslay · Mar 25, 2013

I've redone both ends of the wire just in case it's my fault, the cable tester lights run 1 through 8 in the correct sequence on both parts of the tester at both ends of the wire.

atomicWAR · Mar 25, 2013

any luck working?

bobslay · Mar 25, 2013

No tester thinks it's great but it's not working at all (no lights on PC or router). Ive ordered some shielded cable and I'll test it before I run it

hopefully that should sort things out

atomicWAR · Mar 25, 2013

keep me in the loop. good luck bro

dbhosttexas · Mar 25, 2013

Molletts pretty much hit the nail on the head. It is possible for a cable to test for sufficient continuity and pass the basic test that the meters with the sequential lights shows, and still not be crimped sufficiently to allow the cable to carry signal at full strength / frequency. There are a LOT of variables to this, but the most likely source I would suspect is either jacks that are designed for stranded only being used on solid wire (BAD choice), or simply not being crimped down sufficiently. Try giving each end another good squeeze with your crimpers and try again!

bobslay · Mar 25, 2013

Thanks all, just squeezed both ends till I started to pass out, still no joy. Could it be the RJ45 plugs I'm using aren't that good? But again I wouldn't expect then to work at all in that case.

atomicWAR · Mar 25, 2013

bobslay :

you have yourself an enigma wrapped in a mystery

dbhosttexas · Mar 25, 2013

From left to right, hook unerneath the color pattern should be...
Orange / white, Orange, Green / white, blue, Blue / white, green, Brown / white, brown.

You have verified that you have continuity in the correct order end to end with the cable, so next question. If the signal for the meter is strong enough to light up the LEDs, the signal to / from the NIC / router should be strong enough, but... it might not be...

The cable you used along the floor, is it the same length as the one you are routing in the attic or wherever you are routing? Are you over 100m in total length?

New Cat 5 wire, tests OK but doesn't work.

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