How to check acc wire?

[Redline240]

For awhile now i've been slowly loosing power to my accesories, first wipers, then mirrors, etc...my clock light at stereo would work for a day or two and then not for a few weeks...anyway somewhere along the wiring there's either a loose connection or my ignighter box/switch or whatever its called is gone...all i know is that its the acc/ignition wire thats got no juice...

Anyway, whats the easiest way to check where its loosing its power? Has anyone else ever had such a problem? Any advise would help!

Redline