Bathroom overhead lights work 5% or less of the time


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Old 06-14-11, 02:55 AM
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Bathroom overhead lights work 5% or less of the time

The bathroom has a vent exhaust, heater and light switch in a 2-gang box with 4 cable runs to it. There is a separate light switch in a single gang box below this 2-gang box.

The single gang operates lighting above the bathroom mirror which is above the sink. The 2-gang operates the lighting above the bath tub/toilet area within the vent/heater assembly.

Oddly enough the light over the tub or over the sink will not turn on out of 10 tries, but sometimes oddly after it has "sat OFF for a while" on the 1st try the light will turn on, but will not come back on again immediately following the next "OFF" toggle.

Last night, thinking this is the usual stuff (light switches gone old and broken), I replaced the light switches and I rewired the 3-device proprietary switch assembly to something more common for 3-device's from home depot. All is right and connected in the right place. I then replaced the single light switch as well. Power back on and NOTHING, no lights.

Found 2 bulbs (incandescent) had burned out, 1 above the tub/toilet and 1 above the sink. The fixture above the sink will take 3 bulbs. It also had a fluorescent bulb in it and an unused light socket. The fluorescent bulb would come on "sometimes" over the sink, but it would never turn on over the tub/toilet.

Vent and Heater work fine and appear to share the black "common" to the largest gauge cable run, along with the over toilet/tub light, in the 2-gang box.

I remade all the connections in the light fixture over the sink and I thought that would do it cause they seemed poor to me, as this was a "friend put this in fixture" many years ago before I was around. Power back on and same result.

Using a voltmeter I checked the common black wire terminal screws on the 3 device switch to the opposing device terminal screws. I got just over 120v results on the vent and heater switches and on the light switch I got something like 83volts when its turned on.

When I test voltage from the terminals on the single light switch in the single gang box, to my surprise I get "ZERO" voltage when the switch is in "ON" mode and I get "120v" when its in "OFF" mode. To me this would mean I should see the light turn on over the sink when the light switch is "OFF", unless I'm thinking backwards????? or something suddenly went wrong in the wiring in the wall?????

The 83 volts, correct me if I'm wrong, tells me that the toilet/tub light switch is not passing enough current/voltage to reach the required 120 to light the bulb. No breakers are tripping, but I did end up with two burnt out bulbs 1 from each different fixture that "I guess" share a common link in the circuitry.

The one thing I didn't do, because my back and feet were killing me at this point standing atop the SINK, was measure voltage at the light fixture "source wires" above the sink or measure voltage at the light fixture above the toilet/tub. The toilet/tub light fixture socket surrounding shell around the metal light bulb socket seems to be damaged (a piece cracked off the top side of it), but the metal socket etc.. isn't damaged at all from what I can see.

How would ya'll proceed? Is it likely one or both of the fixtures since I've replaced the switches?

Also, there is another point to make. I'm not sure 100% what is all on this circuit, but there is 1 GFCI circuit in the fuse box and I know that it passes through both bathrooms, maybe the hall light (not sure about that one), for sure the back porch receptacle and an outlet on the shared bathroom to master bedroom wall and the back porch light fixture and another receptacle indoors just opposite of the back porch receptacle on the same wall, but again inside only inches away. TO ME, this sounds like the GFCI circuit is overloaded. It has tripped before, but not in regards to the bathroom lighting problem I'm having.

GFCI circuit - Now we're running an Intex pool pump at night, back porch light and receptacle used a lot, indoor receptacle opposite of back porch receptacle used constantly, both bathrooms frequently are in use at same time and the master bedroom wall socket is barely ever used.

I thought each bathroom was supposed to have its own dedicated GFCI circuit? or is that new code?

Also, one of my surge protector power strips says there is a wiring/line fault in ONE living room wall outlet. I have bought another outlet hoping its that simple, but is it ever?

I'm wondering if all of this is tying together, as I've felt for a while now that this house's electrical was not up to par. If you don't think the GFCI circuit is a concern and don't wanna comment on the line fault in the living room, just give me help with the bathroom lighting problem as its the most pressing right now.

Also, if it makes any difference, I could not get the voltage down to "zero" when I was working on the bathroom light switch wiring. The lowest I could get it by turning off 5 circuits (after much experimentation) was .5 millivolt. I realize thats not a lot, but when my voltmeter leads are held together in an ac voltage test, it comes up with 0.00, so I know that .5 millivolt wasn't coming from my meter. Does that mean anything?
 
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Old 06-14-11, 03:42 AM
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With the switch in the "off" position, you get voltage? Tells me either the switch is upside down, or there is another switch (3 way) in the mix. 83 volts is phantom voltage. You are using a digital meter, correct? If you have access to an analog one, try it.
How old is the house/wiring? I believe the GFCI rulings came about somewhere in the 1993 code, regarding bathroom separation, not sure. If older, then there is no telling what you have. Sometimes remodelers grab power where they can, and it ain't right.
You said one socket had a fluorescent bulb in it. Are you talking CFL?
I am assuming these are can lights over the tub? If your bulb is too large a wattage, it could cause the thermal switch to trip out, and only come back on after it has cooled.
Grabbing for straws, hoping it will help.
 
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Old 06-14-11, 05:30 PM
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How are you reading voltage with your meter, hot to ground, hot to neutral?

When I test voltage from the terminals on the single light switch in the single gang box, to my surprise I get "ZERO" voltage when the switch is in "ON" mode and I get "120v" when its in "OFF" mode. To me this would mean I should see the light turn on over the sink when the light switch is "OFF", unless I'm thinking backwards????? or something suddenly went wrong in the wiring in the wall?????
That sounds as if the neutral conductor is being switched.

Using a voltmeter I checked the common black wire terminal screws on the 3 device switch to the opposing device terminal screws. I got just over 120v results on the vent and heater switches and on the light switch I got something like 83volts when its turned on.
Are these three items on the same circuit or is the light on the same circuit as the other lights?
 
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Old 06-16-11, 11:16 AM
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chandler -
According to the printing on the new light switch, it is in OFF position when I'm reading the 120v and I am probing both light switch screws with my DIGITAL multimeter using the AC setting.

What is "phantom voltage"? I mean, can't 83 volts still jolt ya?

There are no 3 way switches in the bathroom and there is only one 3 way switch in the entire house (living room).

House was constructed early 80's, maybe late 70's.

The light fixture over the sink (vanity) has 3 bulb sockets in it. One 19w CFL is what is in there now and again, it worked yesterday just once after it sat for a long time. Once we leave it on it'll stay on, but will not come back on until you luck out again hours later.

CasualJoe -
Reading voltage hot to neutral with the digital meter.

The vent has its own cable run, sharing to a common black on a 4th cable run. The heater has its own cable run, sharing to the same common black 4th cable run. The light over tub/toilet has its own cable run, sharing to the common black 4th cable run. So all 3 devices in this double gang box share to the same 4th cable run, which is not connected to anything else via neutral or ground. IE: the 4th cable run is just sharing the black line with the 3 devices.
~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~
The light over the "vanity/sink" has its own single gang box and my gut is telling me it is sharing something with the other 3 devices, but
I cannot be sure without ripping the wall out or I guess I could run a continuity test from that box to the double gang box? and see which one its sharing???? From what I can tell too, I think the "lighting" circuits in this house are all wired together apart from the wall outlets, but thats just a "hunch" cause I haven't gone through and tested every single outlet/switch to be sure of that.

Again, there has been no remodeling or new wiring work. The house wiring has been the same since it was built except for the addition of the new light fixture over the vanity/sink. This problem just all of a sudden started happening sometime last week.
 
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Old 06-16-11, 07:13 PM
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CasualJoe -
Reading voltage hot to neutral with the digital meter.
So, what voltage did you get hot to ground? Still sounds to me a lot like the neutral is being switched when I think about your earlier statement.

to my surprise I get "ZERO" voltage when the switch is in "ON" mode and I get "120v" when its in "OFF" mode.
 
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Old 06-19-11, 12:15 PM
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I didn't check voltage from hot to ground. As it turns out it was either the fixture wiring (over the sink) or both that and the wiring to the lamp socket in the light above the bath tub/toilet. The bath tub/toilet light socket had apparently suffered a burnout one day and the neutral wire was black charred/scorched. This is that lil short wire that actually plugs into a socket in the light fixture above the tub/toilet, about 5-6 inches long with a light bulb socket on the end of it. I pulled this out completely to go get a new one and resistance checked all the wiring in the fixture above the sink and messed with those wires a bit and now the light above the sink comes on every try. So, either way, I fixed it. Thanks for ya'lls time.
 
 

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