Need help fixing light switch wiring across two rooms.

9 years ago

A few months ago my dad attempted to replace some light switch plates in our downstairs bathroom and garage, and in the process killed the lights to the garage. What we have is a double switch in the bathroom which controls the two lights in there, and another double switch in the back of the garage. There is one double switch that was left alone which controls both the mudroom light and the garage lights. After he replaced the bathroom switch the lights in the garage will only turn on if the lights in the bathroom are turned on.
The switch in the back of the garage is supposed to control the garage lights and the back porch lights. I had limited equipment but I was able to attach a single switch to the back panel which allowed the garage lights to turn on but at the expense of the back porch light, which turns on when the switch is turned off. I know we need to get a double switch for the back door but my main concern is the fact that the switches for the garage lights (both the one in the mudroom and the one in the back of the garage) only function if the bathroom light is on. There is a new double switch in the bathroom but I am not sure if it is the type of switch or the way it's being wired that is causing this issue.

To recap:

Bathroom (double switch, controls bathroom lights, was replaced, is required to be flipped on for either garage light switch to work)

Mudroom (double switch, controls mudroom lights and garage lights, untouched)

Garage (double switch, controls garage lights and back porch lights, currently has a single switch which alternately turns on garage and back porch lights depending on which direction it's flipped in).

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Comments (9)

greg_2015
9 years ago
A double switch like one of these?

My guess is that the power used to come into the black screw, pass through the tab on the right without going to the switch and exit on the other black screw to continue on to the garage or mudroom or whatever.

The power would also pass through the switch to the lights.

Now, you might have the two sides mixed up so that the power to the garage/mudroom has to pass through the switch.

Do both lights in the bathroom come on when you switch on either switch?

Regardless, the first step is to identify which wire is the incoming power. Which wires go to the lights and which wire continues on to the garage.
Toph Hughes
Original Author
9 years ago
Yes, the double switches look pretty much the same as that image.

No the lights in the bathroom are working fine, both operate each bathroom light fine, but only the switch on the right side affects the power to the garage. When that one goes out, the juice doesn't continue on to the garage.
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greg_2015
9 years ago
Just in case my word description was too confusing. This is the path that the continuous power should be taking:

And this is my guess at the path that the (wannabe) continuous power is currently taking:
greg_2015
9 years ago
So as I said, the first step is identifying the wires.

Remove the switch altogether. Turn the power back on (obviously make sure none of the wires are touching anything). Use a tester to see which wire is live. That's your source.

Turn the power off. Connect the source to one of the other wires with a wire nut. Turn the power back on. What came on?

Do the same thing until you identify everything.
Toph Hughes
Original Author
9 years ago
Thanks so much for the help. I will try that and get back to you if it doesn't work.
Vith
9 years ago
So your dad did it wrong and didnt even test to make sure all was well? Geez... makin us handymen look bad here.
Toph Hughes
Original Author
9 years ago
last modified: 9 years ago

this is what the switch I'm trying to fix looks like.
greg_2015
9 years ago
So it isn't a double switch. It's two switches.

Have you tried identifying the source and destination wires like I mentioned?

It's a bad picture so I can't really make it out. Can you draw a diagram of how it's hooked up?
Vith
9 years ago
last modified: 9 years ago
Well, he double tapped one of the switches, so the other switch depends on that. Need to unhook them and find which black is the live hot. Then wirenut two spare wires to the source and take those to each switch separately to provide constant power to each switch.

I suggest cutting power to the circuit, unhooking the blacks and have them not touching anything or each other and turn on power again and testing with a klein voltage tester to find the hot. This is normally how I do it. Just ensure no one else is going to be in the area or able to touch the wires while you are diagnosing. Cant use a cheap tester, they go bad and give false positives and are also too sensitive to differentiate which wire is hot when they work as intended (they start beeping just getting near the box).