How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Mike G. Your Own Question
Mike G.
Mike G., Master Electrician
Category: Electrical
Satisfied Customers: 7526
Experience:  Proven Professional 48 years Experience
Type Your Electrical Question Here...
Mike G. is online now
A new question is answered every 9 seconds

I have a little mystery on my hands, I have a switch receiving

This answer was rated:

I have a little mystery on my hands, I have a switch receiving current on one wire of a 14-2 cable and sending it back on the other wire of the cable to a receptcle box. The hot wire reads 120 with the switch on and about 33 or so with it off. The only thing I can think of is that I have the two wires short circuting at some point but it should read more than 33. Not sure whats up

Sparky : Hello, my name is XXXXX XXXXX I'm here to answer any of your electrical questions.
Sparky : So, the switch controls the receptacle?
Customer: There's nothing connected yet, it will be a pendan ceiling light eventually. I found voltage in the hotwire regardless of the switch position and so started the mystery
Customer: This is all new romex from the hot and neutral to the box, down to switch and back to box. It ties into old know and tube in a nearby ceiling light box.
What was it for originally?
How many wires are going to the switch? Are there any other wires in the box? If so, what colors are they?
Customer: replied 4 years ago.
The switch box has only a single 14-2 romex cable bringing the power to and then from the switch. The current enters the ceiling box, the neutral stays in the box whil ethe hot goes down the 14-2 cable and back to the ceiling fixture to power the eventual light
Got it. So it's a cold switch, Normally a situation like this is because of a loose neutral. have you verified that the neutrals are all connected nice and tight?
Customer: replied 4 years ago.
The only neutrals are the connection to the old knob and tube style cable feed, the other end of that romex is the loose neutral that is waiting to be connected to the light fixture.

How does a loose neutral produce a reading when the switch is off?
You really don't have a neutral at the switch. You Just have a hot, and switch leg. But when there is a loose neutral all kinds of voltage variations happen. I have seen hot wires way up past 200 volts, and some as low as 11 volts. When you are testing, are you testing from ground to hot?
Customer: replied 4 years ago.
Yes that's correct, no neutral in the switch box, just the switching of the hot wire and bringing it back to the ceiling light box.

I'm measuring the two stripped wires in the ceiling box, the neutral (straight from the connection to the old knob and spool, and the hot which returns from the switch. Both are connected into the circut and the old know and tube wire in a neighboring box
You know I have to admit that I do not have very much experience with the old know wiring. I think I would serve you better by opting out and giving another expert a chance to help you with your situation. Would you be ok with that? Sometimes someone jumps on it right away, other times it takes a while. Let me know. Thank you.
Customer: replied 4 years ago.
sounds good
Have a good night. I will do that now. Thank you.
Hi, I'm Mike and I'll be glad to assist you. I've read the posts and need to know if the box you licked up the circuit at is controlled by 2 3way switches on the knob and tube?
Customer: replied 4 years ago.
No 3 way involvement. I went over to a neighboring ceiling box and connected the black wire of the 14-2 cable into the hot wire of the existing wiring(not the switched hot) and the white wire of the 14-2 cable to the neutral wire of the existing wiring.

The ceiling box I patched into, contained three wires, a hot that feeds the other rooms down the line, a switched hot and the neutral. I'm pretty sure things connected correctly here because the new 14-2 cable that comes into my new work registers hot on the hot wire and nothing ont he neutral wire.
What are you using for a tester?
Customer: replied 4 years ago.
I originally detected current in the return from the switch with a hand held greenlee GT-11, then put the multimeter on the hot and neutral with switch up and then down. For some reason I'm reading 33 or so with the switch in the down/off position
With switch off and the reading you got on the load side of the switch, it is defiantly an open neutral You need to check the white wires ahead of the fixture.
Customer: replied 4 years ago.
Alright, I had no expectation that this could be the case since the neutral carries no current except back from the device and if the switch is off, there would be no current going through the switch.

What am I missing?
circuits on different phases, sharing a neutral will operate if the loads on both are equal and the neutral is open. If the loads have a difference the neutral will carry the difference. The voltage reading you're seeing is the load from another circuit on a open shared neutral. There is no other explanation for it. Check to see if any other outlets are acting abnormally. Check all neutral connections.
Customer: replied 4 years ago.
I can check the box where the connection was madem this is the most likely culprit correct? And a open neutral means that a neutral connection (in the mentioend box or before it) has come "undone"?
Customer: replied 4 years ago.
The connections in the box where I connected the new 14-2 seems fine. Not sure what I was expecting to see, should I be going to the box previous to this one and ensuring that my white is not shared and checking continuity? I was thinking this old knob and spool possibly cracked in the casing when I made the connection and so would appear to be good but possibly not.

Customer: replied 4 years ago.
(Update) I found that the hot and neutral in the ceiling light box are reversed and chasing it to the swich that runs this light I've found that the neutral is being switched via 2 3ways and not the hot.

Does this also match your idea about the open neutral? Or do you think there has to be an open neutral regardless of having the which colored wire is carrying the hot?

OK, that's why I asked about there being 3 way switches. On knob and tube the 3 way are not wired the same as moderne 3 ways. The traveler connections are a hot and a neutral making the common either depending on the switch position. The switches need to be set to provide a hot from one and a neutral from the other for the light to work. If set having both being either hots or neutrals at the same time the light won't work. I suspect that you are on a wire from the switch to the light and it changes polarity and you need to source your circuit elsewhere.
Mike G., Master Electrician
Category: Electrical
Satisfied Customers: 7526
Experience: Proven Professional 48 years Experience
Mike G. and other Electrical Specialists are ready to help you