I have a G5RV antenna. It used to work fine. I had it disconnected for several months. Now I can't get it to load. I think there may be a short or open in the coax. Is there a way to determine how far out on the coax the problem might be? Much of it is under the house and I am disabled.
Many of the newer antenna analyzers have the ability to locate the distance to fault on a coax transmission line. If you do not have one, usually someone in your local ham club is willing to loan one or even come out to assist with the troubleshooting.
With a G5RV antenna, often the problem can be in the window line connections either at the center of the antenna or where it transitions to coax cable. Corrosion from the elements is a typical problem. Unfortunately, this is difficult to determine remotely - you generally need to lower the antenna and do a hands on inspection.
What you are looking for is a Time Domain Reflectometer.
It sends signals down the line, reads the reflections and determines the distance to any impedance changes. See if one of your more well equipped Elmer's has an antenna analyzer with this feature and it will tell you a lot about your setup, including how bad your connections are.