Wiring – wires to outlet died all of a sudden

Here's what's actually going on inside those 3-light testers.

You see there is a neon light between each of the prongs. The red is between neutral and ground for instance. The problem is, neon lights are not voltmeters. They will light for a wide variety of voltages, and won't tell you which voltage except very subtly by brightness.

When they wrote the descriptions for the device, they were forced to come up with something for every light combination. They were optimised for the kind of mistakes seen in new construction... and so they're misleading and wrong when troubleshooting old work. They're so horrible I call them "Magic 8-ball testers"*. The testers are much improved by tearing the sticker completely off, and learning to interpret the raw data the lights are providing.

For instnace, a broken neutral with a load on the circuit turned on. Neutral is pulled up to 120V, so the outer lights light. Interpretation: "Hot Ground Reverse" (unlikely). We've had novices waste hours trying to chase that nonexistent fault.

The ground-neutral tangle is a clue

If the green/ground wire is connected to neutral in any way, That Is Bad. That is often done by incompetent hacks to try to work around a problem, typically one they created.

I suspect that somewhere upstream, the neutral wire is broken. The previous hack decided to bootleg neutral from the ground wire, which is why he crossed them.

Generally, wiring problems are at terminations, and every one of those should be accessible. However every once in awhile you have a problem with the wires proper, e.g. someone drives a nail through a misplaced piece of Romex.

* Amusingly, the randomly assigned Imgur URL for this is 0BSoD.jpg. I couldn't make that up...

Harper is right about trace voltages on disconnected wires it could be anything causing inductance in the wires, but there are few things that concern me.

Aluminum wiring: One of the big problems with aluminum branch wiring is that is has a tendency to loosen up on connections and burn back from the connection point. Then you will be getting weird voltage readings like 57.7 volts. But I don't think this is the case where you have a red and a black reading the same voltage more than likely they have no power connected to them and should be reconnected to the other red and black with 128.4 volts.

You didn't mention if everything was working before you started your pigtail. When you start taking things apart you can start finding things like you have mentioned and we get caught up in chasing ghosts.

Instead of trying to determine each problem as you go along, I would complete the pigtailing first. Then go through and turn everything on and check to see if there are any problems. Look for strange things like a 1 or 2 volt drop between two receptacles that are only say 12' apart. That would indicate a loose connection somewhere. Lights dimming when you turn something on and the circuits are not related. That would indicate a loose or broken neutral. You television only comes on when the dryer is running (true story). Also broken neutral.

Then if you find something acting up you can identify the physical problem and location. Then if you post that problem we can be proactive and not so speculative.