[R-390] GFCI tester

[Bob Camp]

Hi

How much pain and suffering are you willing to put up with? Assuming you are into this:

1) Pull the wires to the circuit at the panel. Unplug everything from the outlets. Ban all traffic from the area.
2) Energize one of each pair (white/black, white/ground, black/ground) and ground the other. Measure the current into the energized wire. Should be zero.
3) Check the current from each un-energized wire to ground (should be zero). 

Grab a current source (DC lab supply):

1) short everything together at the far end of the circuit. 
2) Source current (a couple amps)  between the white and black. 
3) The ground should read 1/2 the voltage on the source end. If not, there's a fault.
4) Source current between white and ground.
5) Voltage on black will be closer to the white than the black. The ratio of the ground wire resistance to the power leads will let you calculate what's "right". If it's not right, you have a fault. 

Let's hope you have found the problem and don't try the next step.

1) combine all three wires at the panel. 
2) energize the set of them and measure current. Should be zero. If not, you have a fault. 

At each "energize it" step, check things with an ohm meter first…..

Once you are done with the tests, put the ground and neutral back where they belong. Remove any short at the far end of the circuit before attaching the hot wire to the panel. Once you are done, allow traffic back into the area.

Assuming that turns up nothing, start pulling apart each and every box and looking for bugs / water / debris and "extra" circuits in the box.  

If you still have no joy, it's time to start pulling new wire. 

Bob