that depends.
does that line read some small voltage, or ground?

if it reads ground, you have a break in the line somewhere and you need to trace it back to the vr from the alt.

if it reads voltage of some sort, then you need to check voltage on the other line plugged into the alt and see if it reads voltage or ground.

again, ground, would mean a break, voltage on both means bad vr, or bad voltage to the vr as I said in the begining.