Ethernet wiring troubles
Discussion
I've been having a go at running Cat5E cables into the loft and on to various rooms with a view of giving a robust network to key parts of the house, but no cigar yet! I ran 3 cables up from the router to the loft (intending 1 to the switch, 1 direct to the lounge, 1 spare), but upon terminating these I find my RJ45 tester says all 3 are defective and none of them will provide a laptop with access to the router (or even flashing lights on the ethernet socket) either. Each cable is about 12m long.
The tester is a split master and slave thing - an AliExpress version of this: https://cpc.farnell.com/tenma/72-9945/network-cabl...
I've ended up pulling the cable from its socket (at the router end) and shorting each pair in turn, then testing for continuity with a multimeter through the plug at the other end, and each core seems good. Sample cores have about 1ohm resistance. No shorts between cores. The plugs have good crimps with no measurable resistance between core and plug pin (they're open-ended plugs so I can check this). My tester works well with other known-good cables (made from the same reel), albeit of shorter length, and the tester has a new 9V battery. The cables are run in parallel with T&E and CCTV coax for part of their length, but there's no change in performance when those circuits are powered down.
The only time I get something positive is if I plug one of the cables into the router and the master tester into the loft end - then LEDs for each core flash in turn, as would be expected if the slave tester were at the router end. I just get a very faint flicker of the LEDs for a couple of cores if the master and slave connected as intended.
I'm stumped. Any bright ideas?
The tester is a split master and slave thing - an AliExpress version of this: https://cpc.farnell.com/tenma/72-9945/network-cabl...
I've ended up pulling the cable from its socket (at the router end) and shorting each pair in turn, then testing for continuity with a multimeter through the plug at the other end, and each core seems good. Sample cores have about 1ohm resistance. No shorts between cores. The plugs have good crimps with no measurable resistance between core and plug pin (they're open-ended plugs so I can check this). My tester works well with other known-good cables (made from the same reel), albeit of shorter length, and the tester has a new 9V battery. The cables are run in parallel with T&E and CCTV coax for part of their length, but there's no change in performance when those circuits are powered down.
The only time I get something positive is if I plug one of the cables into the router and the master tester into the loft end - then LEDs for each core flash in turn, as would be expected if the slave tester were at the router end. I just get a very faint flicker of the LEDs for a couple of cores if the master and slave connected as intended.
I'm stumped. Any bright ideas?
Assuming your tester is working, it is only a continuity tester after all that cycles through the 8 pins + ground (not with CAT 5 though).
The crimps / plugs would have to be the obvious issue and I know you think they are OK but the tester suggests not.
Cut the plugs off and have another go?
The crimps / plugs would have to be the obvious issue and I know you think they are OK but the tester suggests not.
Cut the plugs off and have another go?
Thanks for the replies.
Yes it's solid copper cores - 24AWG. The tester doesn't give an error as such, just that it doesn't flash the LEDs in turn as it should to confirm each core is good. The slave tester does flash one or two of the cores very faintly.
I hear what you're saying about the plugs. I did actually start with cheap nasty plugs that came with my crimper and tester kit - these would often miss a pin or two, so I bought better plugs and replaced them. The new plugs are open-ended so I can get a probe on the end of each wire and another on the pin of the corresponding pin of the plug to validate the crimp. I've just checked this again and contrary to what I said the resistance is measurable, but only 1.3ohm which I'd guess is acceptable?
I've also just checked the tester works fine with a patch lead of ~6m I made from the same cable reel and plugs.
Yes it's solid copper cores - 24AWG. The tester doesn't give an error as such, just that it doesn't flash the LEDs in turn as it should to confirm each core is good. The slave tester does flash one or two of the cores very faintly.
I hear what you're saying about the plugs. I did actually start with cheap nasty plugs that came with my crimper and tester kit - these would often miss a pin or two, so I bought better plugs and replaced them. The new plugs are open-ended so I can get a probe on the end of each wire and another on the pin of the corresponding pin of the plug to validate the crimp. I've just checked this again and contrary to what I said the resistance is measurable, but only 1.3ohm which I'd guess is acceptable?
I've also just checked the tester works fine with a patch lead of ~6m I made from the same cable reel and plugs.
thebraketester said:
They cannot be terminated correctly, is the only thing I can think of.
That was my first conclusion too - but the weird thing is the master tester will flash 1-8 in sequence if the cable is plugged into the router (the master doesn't flash if the cable is not terminated), so I can only conclude that each core is indeed terminated correctly at both ends, though clearly something is amiss...CharlesElliott said:
Assuming your tester is working, it is only a continuity tester after all that cycles through the 8 pins + ground (not with CAT 5 though).
The crimps / plugs would have to be the obvious issue and I know you think they are OK but the tester suggests not.
Cut the plugs off and have another go?
How does the tester actually work? It must be relatively sophisticated to confirm continuity by flashing the lights at both the master and slave displays..?The crimps / plugs would have to be the obvious issue and I know you think they are OK but the tester suggests not.
Cut the plugs off and have another go?
Jamp said:
CharlesElliott said:
Assuming your tester is working, it is only a continuity tester after all that cycles through the 8 pins + ground (not with CAT 5 though).
The crimps / plugs would have to be the obvious issue and I know you think they are OK but the tester suggests not.
Cut the plugs off and have another go?
How does the tester actually work? It must be relatively sophisticated to confirm continuity by flashing the lights at both the master and slave displays..?The crimps / plugs would have to be the obvious issue and I know you think they are OK but the tester suggests not.
Cut the plugs off and have another go?
The upshot is that if there is *any* connection between the pins the tester is plugged into the led will light.
If you short all the pins together the leds will light in sequence.
It only proves there is a return path between pins on the tester.
It is the pins on the receiver that tell the story - these must light singly in sequence otherwise there is a problem.
Jamp said:
I've been having a go at running Cat5E cables into the loft and on to various rooms with a view of giving a robust network to key parts of the house, but no cigar yet! I ran 3 cables up from the router to the loft (intending 1 to the switch, 1 direct to the lounge, 1 spare), but upon terminating these I find my RJ45 tester says all 3 are defective and none of them will provide a laptop with access to the router (or even flashing lights on the ethernet socket) either.
The only time I get something positive is if I plug one of the cables into the router and the master tester into the loft end - then LEDs for each core flash in turn, as would be expected if the slave tester were at the router end. I just get a very faint flicker of the LEDs for a couple of cores if the master and slave connected as intended.
I'm stumped. Any bright ideas?
Connected equipment like routers can give those testers false readings.The only time I get something positive is if I plug one of the cables into the router and the master tester into the loft end - then LEDs for each core flash in turn, as would be expected if the slave tester were at the router end. I just get a very faint flicker of the LEDs for a couple of cores if the master and slave connected as intended.
I'm stumped. Any bright ideas?
Have you fitted the plugs the right way round each time, ie the clip on the bottom side of the plug each time as if the clip is on the top the wires will be in the right order but backwards when the cable is plugged in
Jamp said:
.. and none of them will provide a laptop with access to the router..
Bit random, but have you tried the laptop on a patch cable direct to the same port on the router?I've only done this kind of thing once, wiring up the student house daughter was in, and it just worked. I didn't even have a tester. I did have 'pro' level tools from a relative's company though.
Fresh eyes solve a lot of problems, even just going for lunch or going for a satisfying s
te can clear your head enough for a solution to reveal itself.
A better tester would have told you right away though, it annoys me to follow sparkies who have charged a fortune for a data cabling job then when you quiz them why it isn't working they tell you they tested it with the £5 flashy light tester the wholesaler told them was the bees knees.
te can clear your head enough for a solution to reveal itself.A better tester would have told you right away though, it annoys me to follow sparkies who have charged a fortune for a data cabling job then when you quiz them why it isn't working they tell you they tested it with the £5 flashy light tester the wholesaler told them was the bees knees.
Jamp said:
Hanging my head in shame here... Somehow I'd managed to reverse the plugs in the loft on all 3 of these cables - now I've looked with fresh eyes and so replaced the plugs with the cores sequenced correctly, all is well. Thanks for the input all.
As I thought. With catX cable it’s 999/1000 a termination error, either wires crossed or not crimped correct. What’s really annoying is when the badly terminated cable is outside and up a set of ladders. 
Glad you sorted it.
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