I mean, the simplest answer is to lay a new cable, and that is definitely what I am going to do - that’s not my question.
But this is a long run, and it would be neat if I could salvage some of that cable. How can I discover where the cable is damaged?
One stupid solution would be to halve the cable and crimp each end, and then test each new cable. Repeat iteratively. I would end up with a few broken cables and a bunch of tested cables, but they might be short.
How do the pro’s do this? (Short of throwing the whole thing away!)
Higher end cable testers can show you where the break is, but it will be far more expensive that a new cable.
My TP link switch can detect faults and cable length. I’m not sure it can do both together but it’s possible. Worth checking if you have a switch with those features
Hmm, interesting! I have a Synology switch, gotta read up on its capabilities.
I had an AMD Phenom-II era motherboard that claimed it would be able to do that. OP, you might be able to find an old NIC/mobo that could do this for cheap.
you can rent a time domain reflectometer for this purpose… it sends out a signal and then listens for the echos back and calculates the distance. problem is they arent accurate the first like 500 feet so you have to add a reel of 500 ft of matching cable to the end first. electrorent.com rents them.