[electrical101w]

So heres what going on, both my light about my sink and my overhead range light/fan stopped working. At first it went out, then it came aon a day later, then it went back out and stayed out been weeks now. So today i decided to take the cover off for the switch and take the light down to inspect for any loose wires or damage. So when i got them down didnt find anything except where the light was inside the metal box there is a black mark and on the white wires are dirty black. Im not overly familiar with exactly how my mobile home is wired but for some reason the light switch has a black and white wire and the light has 2 white wires wired to it. I took my voltmeter and at the switch it read 98v while it was switched off and 0v while it was switched on. At the light when you put the switch off it read 98v at either white one is combination with the black wires. and 0v at both the white wires coming to the light. Now keep in mind i have not altered any of the wiring at all before it was working and after it stopped working except today i changed the light switch. At the overhead range light/fan there is only 1 wire going into it and there is no power across the black and white.

 

[psgama]

Whoever wired your light messed up. There should never be 2 white wires going to the fixture. The switched leg is supposed to be black which returns from the light switch to your fixture.

 

[electrical101w]

so i switch one white with a black and im all set to go right? another question, why did it work for so long and just suddenly stop working? the rest of the circut works before this light still.

 

[Jump-start]

so i switch one white with a black and im all set to go right? another question, why did it work for so long and just suddenly stop working? the rest of the circut works before this light still.

No, thats just a code violation. The issue is 1. it looks like something seriously overheated in that box. 2. Those wire nuts appear to be crimps, which I dont know about Canada but would not be used for securing splices here in the US.


My guess is that a splice burned up. All those crimps need to go with the correct wire nuts.

 

[electrical101w]

so having the 2 white wires is ok? btw this is a 1975 mobile home trailer so all the wiring is old, the little marettes you see there or wire nuts you call them are all throughout the trailer, you need to use a pair of pliers to crimp down on the marette and then you can twist off like a normal one.

Also why am i only getting 98v at the light and switch when it is off and also at the breaker panel which is only a few feet away i am getting 121v

 

[bob22]

Looks to me that right cable in top photo is source with left cable going to the switch. White to fixture should have had a black marker on it to relabel it has "hot" IMO.
I guess those are scorch marks on inside of box at top? If so, best get a real electrician in.

 

[gregzoll]

It is actually a Switch Loop. That type of setup is common in older trailers. The scorch marks are from the screws shorting out to the box. The only way to stop that is to either get a deeper box, shallow switch or wrap tape around the switch to keep them from shorting out on the box.

As for the wires for the light, they are a little long. I would use the Ideal Push-in wire connectors, since they take up less space in light boxes, then Wire Nuts do.

 

[Jump-start]

It is actually a Switch Loop. That type of setup is common in older trailers. The scorch marks are from the screws shorting out to the box. The only way to stop that is to either get a deeper box, shallow switch or wrap tape around the switch to keep them from shorting out on the box.

As for the wires for the light, they are a little long. I would use the Ideal Push-in wire connectors, since they take up less space in light boxes, then Wire Nuts do.

No, the box fill looks fine. Most likely one of those crimp ones became loose and over heated. If something shorted the breaker would have tripped. But relax, I still remember you saying circuit breakers do not trip on short circuits :laughing:

 

[electrical101w]

No, thats just a code violation. The issue is 1. it looks like something seriously overheated in that box. 2. Those wire nuts appear to be crimps, which I dont know about Canada but would not be used for securing splices here in the US.


My guess is that a splice burned up. All those crimps need to go with the correct wire nuts.

So i tried changing the marettes today or "wirenuts" i inspected the stripped end of all the wires that were in the marettes and none of them were burnt or damaged. I also decided to try changeing the light with another one while i was there. So if i understand this correctly, when i put the light switch on i should be getting 120v on both of the white wires going to that light correct?

 

[gregzoll]

So i tried changing the marettes today or "wirenuts" i inspected the stripped end of all the wires that were in the marettes and none of them were burnt or damaged. I also decided to try changeing the light with another one while i was there. So if i understand this correctly, when i put the light switch on i should be getting 120v on both of the white wires going to that light correct?

No. At the switch you have the White and Black, which is wired in series to allow power to flow through the switch and back to the light when you turn the switch to on. At that box, there should be one hot wire and one neutral. The other two are the switch, which you have the white that goes to the switch connected on the light, and the black that connects to the light is also tied to the two blacks, which one is the switch and the other set of black and white probably goes to an outlet or something.

It is common to find these types of setups in trailers. Especially the older ones.

 

[Jump-start]

So i tried changing the marettes today or "wirenuts" i inspected the stripped end of all the wires that were in the marettes and none of them were burnt or damaged. I also decided to try changeing the light with another one while i was there. So if i understand this correctly, when i put the light switch on i should be getting 120v on both of the white wires going to that light correct?

Correct. If not the problem is somewhere else like at the switch or line coming into the fixture.

Also, when making up the wire nuts, the white from the switch leg should connect with the other 2 blacks and the black from the switch leg should go to the light. Its not essential for current flow, but essential from a code perspective in that if someone down the road takes off the light they might not know which is the hot and which is the neutral. Have a black hot to the light shows you which wire is hot with certainty.

 

[electrical101w]

ok so why would i be getting 98v instead of 120v like at the panel, the panel is only 10ft away. that may be the reason the light dont work, perhaps 98v will not power a 120v lightbulb? and also why am i getting this voltage when the light switch is turned off(i did a continuity test on the switch before i installed it so it is not upside down)

 

[Jump-start]

ok so why would i be getting 98v instead of 120v like at the panel, the panel is only 10ft away. that may be the reason the light dont work, perhaps 98v will not power a 120v lightbulb? and also why am i getting this voltage when the light switch is turned off(i did a continuity test on the switch before i installed it so it is not upside down)

What type of meter are you using? Capacitive coupling will often cause most electronic meters to register a high reading close to line voltage.

 

[gregzoll]

It delends on what type of meter that you are using. If it is a cheap one, there is nothing to "pad" it, to keep from reading this type of reading. You are seeing what we call "Phantom" voltage, which is caused by the batteries in the meter loading the wire to give you false readings.

I have a Sperry that I use and never have any issues.

Normally you would place a light bulb or resistor between a lead and thr wire you are testing, to get a normal reading.

This explains "Induced" voltage. http://www.reliableplant.com/Read/24723/electrical-testing-safety-voltage

 

[electrical101w]

I have a mtp 1550 as seen here (http://www.primoinc.com/en/product/1254/MTP-1550), but i am familiar with ghost voltage as i am a mechanic, but ghost voltage is usually only a few volts. If i use my meter at the panel on a breaker it will read about 120-121v AC.

 

[TimPa]

when attempting to get a voltage reading "across" the contacts of a switch, the reading will indicate that the switch is closed (0 volts) or open (supply volts), just as you demonstrated. the reading taken across an open switch is measuring the hot with respect to (sensing the) neutral potential through the electrical load. the load may be effecting the reading.

a more appropriate "open switch" reading, when checking for supply voltage levels, would be to measure hot with respect to neutral, or ground (wire or grounded metal box).

 

[electrical101w]

when attempting to get a voltage reading "across" the contacts of a switch, the reading will indicate that the switch is closed (0 volts) or open (supply volts), just as you demonstrated. the reading taken across an open switch is measuring the hot with respect to (sensing the) neutral potential through the electrical load. the load may be effecting the reading.

a more appropriate "open switch" reading, when checking for supply voltage levels, would be to measure hot with respect to neutral, or ground (wire or grounded metal box).

all in all your voltmeter just tells you the difference between each lead, but i still dont understand how putting 2 white wires(aka supposed to be neutral) would power this light and also why i have only 98v there.

 

[TimPa]

a more appropriate "open switch" reading, when checking for supply voltage levels, would be to measure hot with respect to neutral, or ground (wire or grounded metal box).

try measuring the hot wire on the switch to neutral or ground, not the other switch contact as you posted.

if you still have 98 volts, then you need to evaluate the circuit (connections) back toward the circuit breaker.

the wire colors have been mis-used. if it were me, I would use colored tape to re-identify them as you sort them out for your own use.

 

[gregzoll]

all in all your voltmeter just tells you the difference between each lead, but i still dont understand how putting 2 white wires(aka supposed to be neutral) would power this light and also why i have only 98v there.

Look up "Switch loop wiring".

 

[electrical101w]

Look up "Switch loop wiring".

well this helps

but still why am i getting 98v?