My house was built in the 1940s and only part of the electrical has been upgraded. I am trying to replace an old outlet on my screened in porch with a weather resistant GFCI outlet but cannot get it to work. There are two sets of wires coming into the box, each has a black and white wire, no ground wire. Both black wires were connected to the black terminals on the old outlet and both white wires on the opposite side and everything worked fine. Using my multimeter, I found which black wire was the "hot" wire (line wire) and also determined the metal electrical box could act as a ground.

I connected a ground wire to the box and the other end to the ground terminal on the GFCI outlet. I connected my black hot wire to the hot wire terminal on the line side of my GFCI and then the white wire from the "hot" bundle to the neutral terminal of the GFCI on the line side. I then connected the black and white wires from the other bundle to the hot and neutral terminals on the load side of the GFCI (sorry I didn't take any pictures). Unfortunately the outlet doesn't work and neither do the electrical lights downstream of the outlet. I cannot reset the GFCI and cannot get anything to work in the outlets.

I did check the wires using my multimeter and with my red probe touching the hot wire, I will get a reading of 120 volts when touching the neutral terminals on my GFCI and the electrical box. But if I have my red probe touching the black wire on the load side of the GFCI, I won't get any voltage readings. Also, when I take the GFCI outlet out and replace it with the old outlet, it works again.

Does anyone know why I am having this issue? Am I wiring it incorrectly? Is the wiring of my house not correct? Any help would be appreciated.

Thanks, Brian

  • When you say the GFI does not work can you relate a bit more about just what that means? Does the GFI trip immediately upon application of the power from the service panel?
    – Michael Karas
    Commented Oct 25, 2015 at 15:21

2 Answers 2


OK first of all you cannot determine whether the box is properly grounded just using a multimeter. The fact that it reads "0V" does not mean it is properly grounded. The only way to determine that would be to confirm that there is a proper ground wire all the way back to the panel, or to confirm that grounded armored cable is used. In your case I would just forget about the ground and disconnect it, you don't need a ground for a GFCI.

Second, try to get the GFCI outlet working without the downstream outlets hooked up to the LOAD side. If you can get the GFCI working by itself but it trips when you hook up the downstream wires, that probably means there is something downstream creating a ground fault and the GFCI is tripping (as it's supposed to). A common cause might be a neutral wire touching a metallic box or a "bootleg ground" where neutral and ground are connected.

If the GFCI doesn't work even on its own, it's probably defective.

  • 4
    If you leave the ground disconnected then do mark the outlet as having "no equipment ground" Commented Oct 25, 2015 at 18:13

With the old outlet wired in the two black wires were basically directly connected. Likewise the two white wires were connected. Since you mention that there are lights, and who knows what all else, connected downstream from the outlet that you are replacing I think that you should modify the way you are attempting to connect the GFI outlet.

Rather than trying to think that all the downstream circuits should be controlled by the GFI you could try to wire things so just this local outlet operates in GFI mode. To do this you would connect the two blacks plus a black pigtail with a wire nut in the back of the electrical box. Similarly connect the two white wires plus a pigtail with a wire nut. Then connect the two pigtails to the GFI outlet to the respective HOT and NEUTRAL terminals of the LINE side of the outlet.

It will require a separate investigation to determine why the downstream circuits are causing the GFI to trip when you wired it up as you did. That will require determining where all the downstream circuits go and then opening up boxes and circuits to isolate branches. The GFI trips may even be caused by something plugged into one of the downstream outlets or one of the light fixtures.

  • This. Put all the wires on the LINE side, connected as it was originally, and get on with life.
    – Mazura
    Commented Oct 25, 2015 at 22:26
  • Well it depends on whether the other outlets are also on the porch and require GFCI protection.
    – Hank
    Commented Oct 26, 2015 at 0:37
  • @HenryJackson - The other outlets could all be wired as their own standalone GFI units. The only reason to daisy chain regular outlets off the LOAD side of a single GFI is to save cost - a decidedly more important concept in years gone by when GFI's were $50-$70. These days when reasonable GFIs can be had for less than $15 it can be a quite different decision.
    – Michael Karas
    Commented Oct 26, 2015 at 0:42
  • Thanks for the input. I think I am going to connect both black wires to the line and both white to the neutral on line. I don't need downstream to be gfci. Might get an electrician to come out for the rest of the house. Multiple gfci sockets are tripping
    – Brian W
    Commented Oct 26, 2015 at 16:59

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.