I had a problem that whenever I turned on the light over the kitchen
island, the GFCI of one of the outlets would trip. It turns out the
GFCI is faulty, so I replaced it. So far so good.
However, I must have messed up something along the way. The GFCI outlet
is in the same electrical box as the dimmer switch for the recessed
lights. Now, the island lights won't come on unless the recessed lights
are on! And yes, if I dim the recessed lights, the island lights dim as
well. Obviously, this is not what I want
I am 99% sure I rewired the GFCI outlet the way it was before. I am 99%
sure I rewired the island light switch the way it was before (since
this was easier to do, I tried replacing the switch before the GFCI).
But...obviously I did something wrong.
You can see a diagram of the dimmer/ GFCI outlet box here ->
And the island light switch (which is a 4-way switch) ->
I believe the three wires marked as "Back black" in the first diagram
is the same as the "Black left" in the second, but I am not positive
about that (back, left etc. refer to the position in the outlet box,
there are a lot of wires to keep track of....)
A few notes:
- I plugged a light into the GFCI outlet, and pressed the "test"
button. The GFCI tripped as expected, and the light went out. So, looks
like I didn't swap line and load, right?
- The 4-way switch works fine (provided the dimmer is turned on of
course...). In other words, the island lights are off when all three
switches are in the "down" (off) position, and each switch correctly
turns the lights on/ off.
So, what do I need to change in order to make the island lights
independent again? Is it time to call an electrician?
OK, I think I understand your diagram... the labels "Grey front", "Back
Black", etc. refer to the colors and locations of *cables* in the boxes,
right? (Each cable containing several wires)
What I don't understand, though, is how this works at all. The answer to one
question might help: I understand you can't turn the island lights on without
turning on the recessed lights too. What about the other way around -- can you
turn on the recessed lights without also turning on the island lights?
Do you have a voltmeter? That could prove invaluable in tracking down which
wires go where.
Which light? The LED in the GFCI, or one of the room lights?
Modern GFCIs refuse to power up if the line and load connections are reversed,
so you at least have the line wires connected in the right place. That does
*not* prove that you have the right wires connected in the right places on the
*load* side, however.
With the switch for the island lights being in a separate box from the switch
for the dimmer, it's hard -- but not impossible -- to imagine how that might
have become goofed up by changing only the switch.
Dunno, and maybe, in that order. I can give you better advice after I see your
answers to the questions I asked above.
Doug Miller (alphageek at milmac dot com)
Right, "grey" and "black" refer to the color of the insulation of the
It might help to know that the dimmer was added during a recent kitchen
upgrade (~2 years ago).
Yes, the recessed lights turn on regardless of whether the island
lights are on or off.
Yes, I have a voltmeter. I'd be more than happy to measure the voltages
under the various configurations (switches on/ off), but there are a
LOT of combinations. Would really appreciate some focused advice on
what to measure.
To test the GFCI, I plugged a small night light into the outlet. When I
pressed "test", the GFCI tripped, and the nightlight went out. The LED
on the GFCI came on. Pressing reset re-enabled the circuit (LED out,
nightlight on). Note that if the GFCI trips, the island lights also go
Right. My guess is that the electrician (who appeared to be quite
competent, he seemed to know what he was doing) did something creative
to add in the dimmer switch. Also, the outlet was originally a regular
outlet, not a GFCI. He replaced it with a GFCI to bring it up to code
(the outlet is over a countertop, GFCI is sort of unnecessary since the
sink is in the island, but code is code).
Any advice on what to do next?
Thanks for all your help!
For what it's worth, it's vanishingly unlikely that *any* of the cables in the
box containing the GFCI and dimmer has its other end in the box containing the
4-way switch. When controlling a light from 'n' locations, you need two 3-way
switches and (n - 2) 4-way switches; e.g. for 2 locations, two 3-ways and zero
4-ways; for 3 locations, two 3-ways and one 4-way; etc. -- and the 4-ways
*always* sit in the middle, with the 3-ways at the ends. Power goes to one
3-way, and the light is connected to the other. Since the power for the island
lights is clearly routed through the GFCI, there must be a cable leaving that
box and going to one of the 3-way switches -- *not* the 4-way.
Sorry, I guess I wasn't clear -- your diagram does not appear to represent an
electrical circuit that can actually function. Maybe I'm misunderstanding or
misinterpreting it. Or maybe there's a mistake in it -- have you
double-checked it to be sure it accurately represents the reality of what's in
the box? (Referring specifically to the diagram of the GFCI & dimmer wiring)
Interesting. And somewhat surprising.
We're getting there... I still don't have all my ducks in a row yet.
What about the recessed can lights? Do they also go out when the GFCI trips?
Does anything *else* go off when the GFCI trips? Any outlets that go dead?
(I'm betting on 'yes' answers to all of the above)
"Creative" and "electricity" is not usually a good combination. ;-)
That shouldn't matter, I don't think.
Just double-check your diagram, and answer Round Two of my questions... I'll
be back atcha later on when I see your answers. Interesting little problem...
Doug Miller (alphageek at milmac dot com)
Well, I'm no so sure about that. The island lights are on a different
circuit than the dimmer/ recessed lights. I have to turn off two
separate breakers to disconnect both. I assume they share a common
neutral. (yes, this is where I'm glad I have a voltmeter - there is no
way to tell whether the power is off for the island light switch
I've checked it twice, but like I said, there is a LOT crammed into the
box that houses the dimmer and GFCI. I've lost daylight (chicken and
egg problem....) but will re-re-recheck tomorrow.
No, the recessed lights stay on.
Yes, there is an outlet on the other side of the kitchen that goes
dead. One of the three switches that controls the island lights is
above that outlet.
Almost. That is what I found so puzzling about my problem originally
(GFCI tripping when island lights were switched on). They're on
separate circuits, the only common element is the neutral.
Some more info.
1. When the island light switch is OFF, the voltage for both input
("black left" in second diagram) and output ("black right" in second
diagram) is ~80V. It doesn't matter whether the dimmer is on or off,
voltage is the same. I believe this is normal for a 4-way switch when
you measure using a voltmeter
2. When the island switch is ON, the voltage is 0V for both input and
output. Again, doesn't matter whether the dimmer is on or off.
3. If any of the other island light switches are switched on, the
voltage drops to 0V as well.
4. When the dimmer is OFF, the voltage between the two black wires
attached to the dimmer switch is 120V. When on, the voltage varies
between 12V (maximum light output from recessed lights) to 100V (almost
no light output from recessed lights)
5. The GCI outlets supply 120V, regardless of any switch position.
Not to confuse the issue, but here's another piece of information.
There is a second set of recessed lights in the kitchen. The second set
is also controlled by a dimmer (in an outlet box that also has a GFCI).
The first dimmer is located closer to the island switch, so I didn't
notice this before, but....if I turn on the second dimmer, then the
island lights work, even with the first dimmer off. In other words, to
turn on the island lights, I have to turn on the island light switch
and EITHER dimmer.
Shot in the dark (no pun intended): There are a LOT of neutrals tied
together. I can't easily get to it, it's wedged tightly in the back of
the box. If there is a neutral loose, could that explain the symptoms?
Perhaps they *used* to be on two separate circuits... but the fact that the
island lights don't operate *now* unless the dimmer is switched on, too,
proves that they are on the *same* circuit as the dimmer.
Perhaps -- and if their hot wires came from two different breakers, this could
be *very* dangerous. It's imperative that the two breakers be on opposite legs
of the 240V service, otherwise the neutral could be dangerously overloaded.
This is a potential fire hazard.
Interesting. And *very* surprising.
That's actually *less* puzzling. This is an oversimplification, but it will, I
think, get the point across: the GFCI doesn't "know" about loads that belong
to other circuits, so when the second circuit puts current on the neutral that
the GFCI doesn't "know about" it says "Whoa!! I didn't put that there!!" and
Well, it's common, anyway, when you're using a digital voltmeter, or a
high-impedance analog meter. You're reading, in all probability, a very very
low-current (milliamp level) induced voltage that is of no significance at
Seeing a real current (several amps) at 80V anywhere in a circuit that's
supposed to be 120V is a _major_ red flag. I'll bet if you put a test lamp
across the leads where you're seeing that 80V, it won't light up -- and the
80V measurement disappears, too.
2 - 5 sound normal.
Pair of 3-way dimmers.
Good luck! And let me know what you find when you're able to check the wires
again -- especially that neutral.
Doug Miller (alphageek at milmac dot com)
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