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Electrical installation in the United States refers to the process of installing electrical systems in buildings and structures in compliance with the regulations set forth by the National Electrical Code (NEC) and local building codes.

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Double wall switch miswired?

I have a double wall switch for my front exterior light and interior front hall light. I do not know if it is two separate one way switches or an actual double switch. However, my interior hall light must be on in order for my porch light to work. No inside light = no outside light. The inside light, obviously, works without the outside light being on.

Is this a miswired switch problem or a bad switch?


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Bare switches

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Red wire tracks behind other switch…

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…and is wrapped here with purple wire.

Generally in my house I've noticed through other fixture updates that the purple is my hot wire. I don't understand why the red would be wrapped with the purple if it's already got a purple on it.

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In which country is this? In the netherlands the wiring is very easy. You need a serial switch, The hot wire (power) you connect on the marked connection that is (P) or darked copper color. The two other connection goes to the lamp 1 and lamp 2 . The null wire runs in the ceiling and you don't see it by the switch, except when you have there also an power outlet.


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Hi @lizadizzle ,

It appears as though there may be a wiring error.

From your description it seems as though the active wire comes into one switch and the output from that switch goes to the hall light and also to the input to the switch feeding the porch light.

Has it always been like this?

Normally with light switches the active wire comes into the switch(es) and since it is a double switch for lights it should be multipled over to the other switch in the plate. The outputs from the switches should each go to their respective lights.

So it should be that that there are only 3 wires coming to the switches. (although it may be wired differently to this)

One active wire in (multipled to both switch inputs) and two wires out, one connected to each switch. They may all be of the same colour or not depending on how it is wired, either as individual wires or in a cable

Be safety aware if you’re going to examine the connections on the back of the switches. Turn off the circuit breaker or remove the fuse that feeds the lights from the main power box. Then test that BOTH lights DO NOT turn on. Once you have removed the switch plate from the wall/door (watch where you place your fingers or tools), then use a test tool -example only to make doubly sure that there is NO POWER on any of the wires, before you touch them, as assuming that there is no power just because the lights don’t work may be fatal.

If this seems overly cautious it is, call an electrician if you have any doubts at all. Life is precious

Update (10/27/2018)

Hi @lizadizzle ,

IF it is wired as I think it may be, by moving the red wire on the inside switch off the purple wire connection and up to join the other red wire, then the outside light should operate dependant on the outside switch only and regardless of the position of the inside switch

REMEMBER to DISCONNECT THE POWER at the power box if you are going to change the wire position

Here’s an image that shows how I think that it may be wired at present.

This is assuming that there is NO POWER coming in on the brown wire like it should be, maybe because it is broken and that is why the red wire was run between the two switches to overcome the problem without having to run in a new wire to replace the brown wire

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(click on image to enlarge for better viewing)

The green line shows the current path for the power feeding the two lights i.e. you need the inside switch to be operated to feed power to the outside switch.

The red line shows how by re-positioning the red wire (the one from the same terminal as the purple wire on the inside switch to the other terminal with the red wire on the inside switch) that the power to the outside switch is now fed independent of the inside switch (shown by dotted line on circuit drawing)

PS sorry should have added that the circle with a cross in it is a symbol for a lamp just in case you’re wondering what is it and also the symbol after the lamps is just an Earth or return path symbol - incorrect I know as it should be a symbol for the Neutral wire but it will suffice for the circuit as it operates the same way.

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Yes it's always been like this, just kind of dealt with it since we bought the house.


Hi @lizadizzle ,

I agree that the wiring looks wrong.

I can draw a circuit that make the lights work as described by you and the pictures provided by you but to do this the purple wires are NOT the power wires but are actually the wires to the lights from the switches. A red wire (inside switch) and a brown wire (outside switch) would have to be the power wires and there is also a red wire going only between the two switches.

If this is correct then perhaps the reason it was done this way is because the brown wire (outside switch) is faulty and there is no power coming in on it. So a red wire was inserted between the inside switch (same connection as the purple wire) and the outside switch (same connection as the brown wire) to obtain power for the outside light.

It should have been connected to the other red wire on the inside switch and not the purple wire i.e. 2 red wires on one terminal, 1 purple wire on the other terminal.

If there is power coming in on the purple wires then I don’t know how it would be wired to make it work the way it does. The wiring to the switches and to the lights would definitely have to be checked out to find this out.

Working on electrical wiring is potentially lethal, call an electrician and get it checked out by an expert


I was just looking at my photos again and yes, I think you're correct on this particular switch where the purple wires are going to the appropriate fixture - not the hot wire. I wonder, if I moved the red wire from the post with the purple wire on the inside switch to the top post on the inside switch, where the other red wire is - will I still need to have the interior switch on for the exterior to work? I can't make it work in my head lol :)

I'll probably end up just calling an electrician like you say, mainly because this is rapidly becoming more than an annoyance.


YESSSS!!! I moved the red wire as discussed and success! Thank you very much for your time and help!


Hi @lizadizzle ,

You're welcome.

Glad that it worked out OK.



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I’m not an electrician but I have done more than my share of home wiring. You need to tread carefully here so you don’t make any errors which could go against your local electrical code.

Do you mean a 2-gang setup or one unit that has two switches built in? Also, does the box have additional wires coming in/out to carry the supply elsewhere in the house (not just the lights)? All of this has an impact on how the wiring should be done.

However, in a nutshell, it sounds as if the wring is setup such that the hot for the outdoor light comes from the switched condition of the indoor light. Unless there is/was a specific reason to do this, it seems highly unusual. Check out this Google page that shows various images and videos, they should help out. If you’re unsure, contact an electrician. Hopefully there’s one in this forum who can give you a more authoritative answer.

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I believe you're both correct. See above for pics now added.


I've never seen a purple wire before but that could just be because the electrical codes are different. I'm not good enough (nor certified) to be making recommendations based on pictures. IMHO, the wiring is done wrong. I'm sure I would figure it out myself if it were in my home but I don't want to guide you incorrectly.


No problem lol I think I'm going to just throw the master breaker and see what happens when I undo the connecting red wire.


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Elizabeth Thompson sera éternellement reconnaissant.
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