Originally Posted by samiller1980
i am not sure what you mean about being connected to the load screws
A GFCI receptacle has two sets of terminals plus the green screw for the ground.
Two of the terminals are labeled "Line" and the other two are labeled "Load".
usually, a new receptacle has a label over the Load terminals warning not to connect power to these terminals.
Power must come in to the LINE terminals, and downstream receptacles must be wired to the LOAD terminals if they are to be protected by the GFCI. But as Jerryh3 said, downstream receptacles may be wired to the GFCI's LINE terminals if only single point protection is required. In this case, the downstream receptacles are not GFCI protected. Only the GFCI receptacle itself is.
The most likely cause of your problem is a bad connection, which would present as a high resistance. If your measuring device draws some current, then it will cause a drop across that resistance, thus the lower voltage. When you plug something in, it will present a much lower resistance, thus all of the voltage is lost across the bad connection (high resistance).