Simple light switch that has black, white and red wires

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Old 01-10-16, 08:43 PM
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Simple light switch that has black, white and red wires

I have an outdoor light that is controlled by one switch. The previous owner had a wall timer installed to turn the light on and off automatically. The switch has died (appears to be a bad solenoid) and I am wanting to simply replace it with a simple on-off switch since I don't really need the timer functions.

Since this is the only wall switch controlling this one outdoor light, I thought it would use a basic single-pole switch. However, when I removed the timer switch, it revealed black, white and red wires. My question is which wires do I use? I took a meter to the wires and saw about 56v across the black and white, 68v between the red and white, and a full 120v between the red and black.
 
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Old 01-10-16, 10:40 PM
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Welcome to the forums.

Logic would tell us that your three wires would be....
White - neutral
Black - hot
Red - load (outside light)

That means you should measure 120v from white to black.
120v from red to black. (if you took the bulb out - you wouldn't measure this anymore)

Your single pole switch should connect to the red and black wires. Cap off the white.
 
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Old 01-11-16, 06:01 AM
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How many cables are in the electrical box containing the timer? Which cable and color wires do the timer input wires connect to? Which cable and color wire do the timer output wire connect to? It makes a difference because someone has connected wires of a different color in the electrical box containing the light or the timer. The lamp should be connected to a non-switched white wire that is AC neutral.
 
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Old 01-11-16, 09:59 AM
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You have only looked at half the circuit. The other half is at the light. Without knowing the whole circuit we can only make an intelligent guess. PJ has done that and told you how to verify. If you want to verify further look at the other half of the circuit.

PJ wrote:
That means you should measure 120v from white to black.
120v from red to black. (if you took the bulb out - you wouldn't measure this anymore)
Equipment note if you are using a digital meter it is possible to get false readings. Readings less than 100 volts are suspect.
 
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Old 01-13-16, 08:52 PM
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Thanks for the tips. I'll take a look at the wiring in the box as well as on the light side this weekend to see what's there.
 
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Old 01-23-16, 01:22 PM
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So I finally had the opportunity to take a look at the outside light connections. It's a basic connection (black and white) and no pigtails inside the box connecting other to other runs.

I also managed to borrow someone's non-contact voltage tester to check the lines at the switch side. What I found was voltage on the red, nothing on the black, and very low voltage on the white (the tester also detects low voltage). Since white is usually neutral, I'm assuming red is line and black is the load side. Looking inside the switch-side box, all three wires run into the wall. They are not pigtailed to other wires. As this house about ten years old the wiring should be up to code and should not have been altered.

Rather than guess which two wires to connect to a single pole switch and risk something nasty to happen, I tried another timer that had line, load, and neutral connectors. I wired the switch up to what I thought it should be but got nothing.

Suggestions?
 
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Old 01-23-16, 01:57 PM
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Does all 3 wires come from single cable or 2 different cables?
Usually red wire is used as load, but since you stated you measured 120V between red and white it might actually be a hot line.

If you see only black and wire wires in the light, there must be a 2nd set of cable somewhere. It might be at switch junction box or it could be in some other junction box that wire from switch junction box was extended or tapped from.

Since you measured 56V between black and white wire, there may be something else wrong. (loose wire in junction box somewhere?)

Pictures might help.
 
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Old 01-24-16, 04:54 PM
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So I had a closer look at the wiring on both the switch and light fixture end.

On the fixture end, it's just the black and white wires (plus ground, of course). There's no other wires inside the box.

On the switch side, it's a junction for several wires. (As far as I can tell, in addition to the one outside light this circuit also includes an interior 4-way hall light, the door bell and two outlets.) Rather than try to photograph the labyrinth of wires, I drew it out. Hopefully this makes sense. There's four sets of cables running into the box. The diagram will show the red, white, and black wires that I'm trying to figure out. The hot wires are indicated in the picture. I've left the ground wires out for clarity sake.
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Old 01-24-16, 05:03 PM
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I removed the timer switch, it revealed black, white and red wires.
At the timer you have A three wire cable dedicated to the outside light.
Outside you have a two wire cable.

That tells us that there is another splice box or switch in that line. If you have a three wire cable at the switch...... then it should be at the light. If it's not at the light..... it's somewhere.

Your latest diagram is of little help if you don't label what each cable is for.
 
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Old 01-24-16, 05:38 PM
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I did some additional digging for another splice box. After some testing of the wires with a line tester, it appeared that the correct lines to connect to a single pole switch would be the red and black and to cap the white (as what PJ originally suggested!). Tried that and, voila, all is good!

Thanks to all for your suggestions :-)
 
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Old 01-24-16, 05:58 PM
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It appears you have conduit with individual wires since you also have a blue wire.
If it was in the conduit with individual wires then you can have different sets of wires in the light.
I'm glad you got it working.
 
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