I think you do have loose neutral connection.

Have you checked the neutral for this line in the main circuit panel?

A rodent or something else - could have 'severed' your neutral line.

"A circuit in my house suddenly stopped working - no tripping of a breaker..."

A neutral has either an extremely loose connection, or it broke for some reason.

The 3 prong tester states "open neutral". You give various voltage readings from your meter. You can get a voltage reading from a POTATOE and a NICKLE sitting on a desk...

Votage is just a difference of potential. The fact that you read 30v on Neutral to Ground indicates a broken neutral wire. It could be a loose connection, but I wonder why a connection got so loose as to suddenly quit all conduction of anything with any type of load. A voltage meter essentially does not put any load onto a circuit.

Since the circuit quit totally and suddenly, an earthquake, house movement, a nail from a picture frame, or a rodent - has basically probably severed your neutral.

Hot to Neutral: 87V Again - a basically severed (where the two broken ends now 'touch') neutral could easily give you this reading...

If it is just a loose connection, you can fix it by tightening. If it is a broken Neutral wire (for who knows what reason) than you will have to either open up the drywall and run new wire yourself; or have someone else run new wire.

AND it is dangerous. A broken wire can be arcing - which raises the potential for fire. If a rodent is working on your home - he/she will also be doing other wiring work.

So - for however, or whatever is causing it - it needs to be found and corrected - asap.

I may have fixed the problem...the circuit in question is more complicated than I thought with a couple branch circuits that I had to chase down. Then I basically removed the first fixture in the circuit (a ceiling fixture). Someone else had told me that if the problem was with a fixture or load, then only those fixtures downstream would be affected...and since this first fixture wasn't working, I started there. I had already checked the neutral connection for the circuit at the panel and it was solid. So, anyway, after removing that fixture, everything else downstream started to work. So, now I'm reconnecting the fixture and hopefully all will continue to work. I guess the issue was a bad connection in that first fixture.

Thanks again.

Since the entire circuit was bad (nothing was working, and all outlets and fixtures were showing the same weird voltage readings), I checked the neutral connection at the panel, and it was rock solid.

So then I followed the circuit to the first fixture (one of those pull-chain ceramic bare-bulb fixtures) and found a branch circuit coming off that fixture's j-box, in addition to the main circuit continuing downstream). So basically there were three penetrations of Romex into that box, and therefore four neutrals wire-nutted together (the neutrals from the three Romex penetrations plus the fixture's neutral.) The connections looked twisted together very solidly...HOWEVER, something was amiss. The wirenut (which looked plenty big for the four wires) was slightly melted, and a couple of the neutrals were pretty badly singed. I saw no evidence of bare wire exposed beyond the wirenut, or any evidence that the neutral had made contact with the metal shell of the j-box.

Anyway, I removed the melted wirenut, clipped away the singed ends of the neutrals, and re-did the connection with a new wirenut, and then taped the open end of the wirenut. That done, the circuit appears to be OK now (normal voltage readings from H-N, H-G, and N-G...with one weird exception - another downstream ceiling fixture (same ceramic, pull-string type) won't operate some of the light bulbs I put in it. I've tried a couple CF bulbs which won't work and a couple filament bulbs (some of which do work and some of which don't). Bulbs that don't work in that fixture do work in other fixtures on other circuits. I checked H-N voltage in that fixture and it is normal.

Weird. Thanks again. Any insight into what might have caused the singed neutrals or the malfunctioning fixture downstream would be greatly appreciated.

Yes, several things can cause the above... Among them:

1. Too much current.

When using the circuit, wires heat up. So does the electrical wire nut. Heating and cooling, can cause the wire nut to loosen. A loose wire nut has more resistance. More resistance creates more heat. More heat eventually toasts the wire nut connection.

2. You could have too much current for the size and rating of the wire nut being used.

3. Loose wires arc among themselves. Arcing causes heat...

3. The lamp fixture which only lights certain lights, and not others - probably has some significant corrosion issues with it. It definitely has significant electrical contact problems. You should replace the fixture.

4. Wire nuts are great. But because of this type of problem; I sometimes have used "Split-Bolt Connectors" manufactured by Thomas&Betts or such.

They come in different sizes. Take a look at the 8H-B2 for example. These things are avialable at HardWare stores such as HD or Lowes.

They need to be properly wrapped. I use a good measure of rubberized, waterproof electrical tape, and finally top it off with the normal vinyl stuff... But these connections properly done - won't work loose.

Not necessarily recommending the above for your situation. That wire nut lasted for quite some time...

It is extremely fortunate - that you have found and corrected the problem! Kudos & congrats!

Some old light fixture sockets were a bit unforgiving in the tolerance specs. Check the good bulbs that won't work there for bigger solder bumps where one of the bulb wires meets the top of the metal screw thread base near the glass. This can jam in the socket and stop the bulb fully seating. The center contact tab in the bottom of the light fixture socket may also have been pushed down beyond the point where it will spring back enough to contact a poorly seated bulb. While it is possible with a bit of luck to raise this tab back up a little if necessary, it is usually less trouble to just find a good bulb or clean up the solder blob on a bad bulb with a small file so that it will then work.