Is my lan cable damaged?

[Launch_pad]

I have a router in my cellar and two lan paths out of the cellar to rooms in higher floors. My main PC connects directly to the router - internet no problem. If I connect a computer to lan1 then I get the same internet no problem, but on trying the third connection I get the message that the IP connection is not recognised (with a 10mps transfer rather than 100) and no internet.
I tested using exactly the same cables between the router and the lan1 and the lan2 to remove any possibility of portable cables being the problem (same between the lan1 and lan2 outs to the same connected computer).
The question is whether the lan cable 2 has been damaged, or could this be caused by something else that Im not network proficient to recognize - there is a huge amount of building work behind the cables (so they are impossible to replace without levelling the house) and I really need to use lan2 as an access point to make my house more wifi friendly.
Any guidance appreciated.

 

[jsmithepa]

Behind-walls LAN cable are unlikely to be the culprit if it used to work. I mean they don't move, unless you had a recent renovation. The troubleshooting is very simple, it's a PIPE, made out of several components, so you replace everything in the PIPE and that should tell you whether the PIPE is the problem. Take the PC next to the router, buy a very long patch cord, very cheap at monoprice.com. etc. The first thing I suspect is a recent software upgrade to PC, are you running W10?

 

[bill001g]

Have to agree with the above in wall lan cable generally never fail after they are installed and working correctly. The actual wires in the wall would have to be damaged by some external source. I guess a nail could have been driven into one or a rat chewed on the cables.

Unfortunately only profession cable installers can afford the meters to test and detect failures in the cables. They will actually tell you how many feet away a break it. Still it does not matter these meters cost $1000 and can go to many times that price.

So if you are really sure it is not your patch cable or your end device you are just going to have to blindly try to find it. In most cases cable problems are the terminations...ie the wall jacks. You could try to remove the wires cut a inch or so off and repunch them down to the keystones. You could I suppose also buy net keystones.

After that you are stuck with the issue that it might be in the wall and generally all you can really do is run a new cable and abandon the old. You will likely never see/find any damage when you do not have a meter...even if you do have a meter many times telling you it is broken at 20ft away does not help when you do not know the actual path of the wire in the walls.