| This
is a puzzling situation, but I can think of at least one
incorrect wiring scheme that would cause these symptoms.
First of all, let me make
some predictions:
If you were to remove the
cover plate on the switch/receptacle combo unit and look
inside, I'll bet that you'll find only ONE cable (with two
individual wires, one black, one white) entering the junction
box. It might be necessary to unscrew the switch/outlet combo
device to get a good view inside.
The combo unit should have 3
screws on it: two gold (for the hot connections) and one
silver (for the neutral connection).
I also predict that there is
a jumper wire from one of the gold screws to the silver screw.
While there may be a white
(neutral) and black (hot) wire entering this junction box,
both wires are actually hot (assuming I'm correct about there
only being one cable in the J-box). This is what I call the
"Remote Switch" method of wiring a light switch, and
it simply means that there is a "hot-at-all-times"
cable at the J-box for the light fixture, and then a single
cable is run to the J-box for the switch. One wire will be
hot-at-all-times, and the other wire will be hot when the
switch is closed (on), thus completing the circuit and
energizing the light bulb.
With this "Remote
Switch" method there is NO WAY that a receptacle can be
properly supplied with hot and neutral wires, so there is no
point in using a combo switch/outlet device. But some
knucklehead did it anyway.
I figure that by connecting a
jumper from the "hot-at-all-times" wire to the
silver screw, the outlet would be energized when the switch is
OFF.
BUT... whatever device is
plugged into that outlet will be in a SERIES circuit with the
light bulb overhead. This is the way Christmas tree lights
were wired in the old days... one bulb burns out and the
others won't work.
Loads are not supposed to be
wired in series.
You have a power-sharing
arrangement going on because of this series circuit. The fan
has a lower resistance than the light bulb, so the fan gets a
larger proportion of the power. But the fan doesn't run at
full speed because there is a voltage drop across the light
bulb. Since there is a small voltage across the light bulb,
the bulb will glow dimly.
When the night-light is
plugged in, it appears to work normally because it has a very
high resistance (a 4-watt night-light bulb would have a
resistance of 3600 ohms, while a 60 watt bulb would have a
resistance of 240 ohms) When the overhead light is off there
is still some current flowing through it, but not enough to
make the bulb glow visibly. If you unscrew the overhead light
bulb, the night-light should go out, according to my
hypothesis.
Also... if you plug a lamp
into the outlet, with a bulb of the same wattage as the
overhead bulb(s), then when the switch is off both the lamp
and the overhead light will glow equally, but not as bright as
normal.
What should you do?
This is a code violation. If
you (or a subsequent owner) runs a motorized appliance with
this plug, you risk burning out the motor because it is not
receiving full line voltage.
1. The switch/outlet combo
could be replaced with an ordinary switch. I suspect there was
a plain switch installed originally, and somebody decided to
try installing a switch/outlet combo, and figured out a way to
make it work even though there are not the proper hot and
neutral wires supplying the junction box.
2. You could replace the
2-conductor cable with a 3-conductor cable, thereby providing
the hot and neutral wires, and also the switched wire to
control the light bulb. This job could be a hassle if you
can't easily access the wiring.
3. You could do nothing, and
ONLY plug the night-light into the outlet, and everything
should be fine. However, I don't recommend this because if
anybody else ever uses that room (like visitors, the next
owner, etc.) they might plug something else into that outlet.
Personally, I'd just replace
the combo unit with a plain switch, and put a night-light in
another outlet.
Bruce W. Maki, Editor.
|
