Electric mystery - any ideas?

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At my friend’s early 70’s house with an outlet and switch in same box. No ground wires. Outlet feeds switch that goes to over the kitchen sink light. Has worked fine for years, then light and outlet both quit. My meter with probes in outlet read 122v on wires and in the outlet, but plug in lamp, coffee pot, or nightlite and they do not work. When I flip light switch, meter reading drops to around 25v. Turn switch off and voltage returns to 122v. So, I changed out to new outlet and new switch. Wires checked and tightened. Same results although now switch only drops it to about 45v. Seems the problem must be the old light fixture. Changed it out to new LED fixture. Same problem except voltage now drops to 67v and new light does not work. Now the rest of the mystery. So I plug in a regular lamp into outlet and it turns on normally. Then flip switch and light works perfectly. Turn on and off, plug and unplug repeatedly and everything works as it should. My question is what caused voltage drop when switch flipped? A short should cause circuit breaker to pop. And how did it miraculously heal itself? Do LED fixtures have a capacitor or something? Did plugging in the lamp do something to the tamper resistant feature that fixed the problem? I don’t think so, but no other idea why it suddenly seems perfect. Thank you for any helpful information from your experience.Burt _____________________Miller Syncrowave 250Millermatic 211Miller 375 Plasma Cutter Hobart Handler 12010FtDrillBit.com
Reply:I am going to guess there is a poor neutral connection upstream which will rear it's ugly head again. I have seen GFCI's that don't fully close the neutral sometimes, it's always those crappy ones with the red and black buttons. If you measure power and it's there but nothing works it's got to be the neutral. Awful strange that a seventies house would not have grounding wires, that started around 1960.Last edited by bigb; 6 Hours Ago at 09:48 PM.Miller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:If it was me I would look at the circuit feed from the breaker out. It sounds like a loose connection on one the wires feeding the outlet. The reason it healed itself with the regular lamp is that it drew enough current to cause an arc at the loose connection and made contact for a while.
Reply:Thanks BigB and JD. I think the neutral must be problem too. There is a wire nut splice from outlet neutral to fixture neutral. I’ll check that tomorrow. BTW, other outlets upstream seem to be fine which tells me it is in this box/connections or else a mouse chewed wire between switch and fixture.Burt _____________________Miller Syncrowave 250Millermatic 211Miller 375 Plasma Cutter Hobart Handler 12010FtDrillBit.com
Reply:Squirrel eat the wire coming to meterCall power company Dave  

Originally Posted by wb4rt

At my friend’s early 70’s house with an outlet and switch in same box. No ground wires. Outlet feeds switch that goes to over the kitchen sink light. Has worked fine for years, then light and outlet both quit. My meter with probes in outlet read 122v on wires and in the outlet, but plug in lamp, coffee pot, or nightlite and they do not work. When I flip light switch, meter reading drops to around 25v. Turn switch off and voltage returns to 122v. So, I changed out to new outlet and new switch. Wires checked and tightened. Same results although now switch only drops it to about 45v. Seems the problem must be the old light fixture. Changed it out to new LED fixture. Same problem except voltage now drops to 67v and new light does not work. Now the rest of the mystery. So I plug in a regular lamp into outlet and it turns on normally. Then flip switch and light works perfectly. Turn on and off, plug and unplug repeatedly and everything works as it should. My question is what caused voltage drop when switch flipped? A short should cause circuit breaker to pop. And how did it miraculously heal itself? Do LED fixtures have a capacitor or something? Did plugging in the lamp do something to the tamper resistant feature that fixed the problem? I don’t think so, but no other idea why it suddenly seems perfect. Thank you for any helpful information from your experience.