Ethernet Parameters

[Garthhh]

Cat5e is good for 100 meters/yards
How much do I subtract for each connection[rj45 punchdown]?
Any ways to determine signal strength?

I have 2 lines that run 50+ yards
One stopped working
I don't find an open with an ohm meter
One line is fine, on the other
I have a connection indication, but no internet

[falldown]

You can get a cable tester, but it sounds like you have a bad cable or a bad port on your router.
Have you tried other ports?

[lwfitz]

Agreed, sounds like a port went out on your router or your cable went bad. Probably the easiest test would be to switch ports on your router and see if that fixes your issue.

But to answer your question, I cant find an exact amount of loss for each connection but cat5e/cat6 on a direct line are good up to 295 feet. Your run of approx. 50 meters is only around 164ft, so I doubt distance loss cuz of connectors is the issue.

Was this line working and then just went dead? 

[Garthhh]

I've confirmed that the ports all work, on 2 different computers, one close, one far
A simple tester is continuity
http://www.amazon.com/s/ref=sr_pg_1?rh=i%3Aaps%2Ck%3Acat5+cable+tester&keywords=cat5+cable+tester&ie=UTF8&qid=1360006159
Which is good with a regular ohm meter
Really doesn't mean much @ 100mhz

I have 3 Cat5e cables running from my house to an out building
1 working
1 not fully working
1 for a couple of phonelines

I pull in a new cable, but it wouldn't be fun...
The problem presented after a power outage, storm

I suspect. Low signal from the modem/router, which is from the isp

[lwfitz]

Its possible that the power surge caused by the outage killed that length of cat5 or one of the connectors but your right, at this point with that info Id focus on the router/modem/signal strength.

Are your other lines stable? No drop in signal when under a load?

Is this dsl? Can you go to the box (if there is one) on the outside of the building where the dsl line comes in and try plugging a phone into the test jack? See if theres any interference that you can here. Maybe a short on the line causing low signal. Plus if you can confirm its before where it comes into the building then it becomes their problem not yours.

[Garthhh]

my isp is my phone company, I'm set up so I can have the modem either place
the phone line is fine, brand new wire from their box
the present modem location is ideal as it gives me better wifi coverage

were I able to determine which wire or pair is bad on the questionable cable, I could substitute a pair from the phone cable...

[lwfitz]

Just giving you ideas 

Next step would be to contact your isp then and explain the issue your having. Maybe a refresh of the signal can fix it.