A neighbor asked me to look at the GFCI receptacle in her garage. She said it tripped and she was having trouble resetting it. The box contained the GFCI receptacle and a 3 way switch for the overhead light. There was an old cloth covered wire coming into the bottom of the box from the basement and 2 wires coming out of the top - one old cloth covered 3 conductor for the light and a newer run of white 2 conductor Romex that went up to a junction box. She said she was pretty sure that everything else in the garage worked fine. (overhead light, freezer, GDO, GFCI on the other side of the garage, etc.)
I pushed the reset button and the GFCI chattered while I was pushing it. It did not reset. I pushed it again and all it did was chatter.
I removed the switch plate to see what was going on and saw that there was nothing on the load side of the GFCI. Well, if there was nothing on the load side to trip it, the GFCI itself must be bad, right? So I told my neighbor I would back with some tools and a new GFCI receptacle.
When I unscrewed the GFCI, I found that the neutral pigtail to the GFCI was loose in the wire nut. This wire was actually a black wire labeled with scotch tape as WHT. In fact, it pulled out of the wire nut when I moved the GFCI. When I tried to remove the wire nut from the neutral bundle, it wouldn't even turn. Here's what the neutral wires looked like after I used pliers to remove the wire nut.
On the left side of the photo, you can see the edge of the GFCI and the black wire with the tape on it designating it as WHT. There is some kind of white coating on the wire, perhaps white paint. Notice the blackened scotch tape as well as the blackened ends of the all of the neutral wires. The exposed copper of the GFCI neutral pigtail is discolored and green with corrosion. On the top of the box is the blackened wire nut from the neutral bundle. All of this discoloration looked like it had been there for a long time. My neighbor said she has used the GFCI on a regular basis, right up until it tripped last weekend.
The two original neutral wires were twisted together, but the neutral for the GFCI and the neutral for the newer run of Romex were just laid next to the twisted wires and wire nutted on. Obviously, they were either never very tight or had worked themselves loose over the years. I found that the same "technique" had been used for the hot wires - the two original wires were twisted together but the new wires were just wire nutted next to them with no twist.
As long as I had the new GFCI, I installed it. I also a replaced the stranded green ground wire, a stranded hot pigtail to the switch and I used a piece of white wire for the GFCI neutral. All wires were twisted together before the wire nuts were applied. Hopefully, there will be no more chattering now that all connections are secure.