If somebody could help me with this, please! There are two switches in a box. I wanted to put a timer on one switch, so I disconnected it. Then I realized that the timer needs a neutral and there is no neutral in that box. So I reconnected the switch but now one switch is depended on the other. Here is my puzzle. There are three wires, white, black and red, I am not even sure which one is hot, but there is obviously one hot and two are loads (lights). So which one is hot?? I connected black to both switches and one switch to white and another to red. The results is one switch turns on lights only if the other switch is on. I reconnected to the white as common - the same thing. Maybe red is common, but something is fishy here, as I don't remember it being common. So how I determine for sure which is hot and how to make sure the switches are not influencing each other Thank you in advance

  • Can you post photos of the inside of the box please? Feb 4, 2020 at 3:58

3 Answers 3


White is hot, per NEC.

However your installation is already a code violation, so it might be two. Also, this particular instance is one of those rare times experimentation does not hurt; switches either short their terminals or do not, so you have already seen the worst case symptom. So go ahead and try all 3 possibilities.

The hot wire is the one that is split to go to 1 terminal on each switch (doesn't matter which). The remaining 2 wires each go to 1 switch, on the remaining terminals.

Here are the relevant Code bits:

  • in a cable, if the white wire is not needed for neutral, it can be re-marked for use as a hot. It must be marked with paint or tape and the tape must be a valid hot color (not white, gray or green). Black is fine.
  • A re-marked white wire must be always-hot, if always-hot is one of the wires in the cable.

As to your timer problem

Either GMOs, vaccines, Roundup, or HFCS is turning young people's wrists into things that can only hold phones. However, for those of us with wrists, we can use a traditional (if 1980s is defined as "traditional") timer. These don't need neutral for power, because the power comes from the aforementioned wrists.

These come in a variety of runtimes, and you can choose a model with or without a "continuous hold" position. These have 2 screws and install like a plain switch. (The cover plate is NOT Decora, it is very clever but weird, and you must, must read and follow the instructions. NEC 110.3(B).)

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  • thank you for answering. The wires are not marked and I have to determine which one is hot and which are loads, well, two are loads, so I need to know which one is hot. Also I think hot goes to the bottom of the switch and load wires to top. But I need to know which is hot for sure. The timer I need is for outdoor LED lights to be on at night. But now I just wanna put the switches back correctly. Do you know how can I determine which one is load and which is hot without turning power on at the breaker, I have a simple tester I can use on live box, is it the only way to test which is live?
    – user111959
    Feb 4, 2020 at 2:45
  • 2
    On plain switches, nobody cares which terminal gets which wire. The important part is the hot wire is split to both switches, and the other wires only go to 1 switch. Since you have already tried one combination and only 2 more remain, I am OK with simply trying all three. I don't bother measuring in a case like that. @user111959 Feb 4, 2020 at 2:59
  • 1
    To find the "hot", connect any two together - if the load lights then one has to be hot. Swap one wire for the unused one, if the other load lights then the unswapped wire is hot...
    – Solar Mike
    Feb 4, 2020 at 10:39

swap the wire that goes to both switches with the wire that goes only to the switch which currently controls both lights.

This because, hot must be thw wire that currently goes to the switch that is master. it the place it should go to is common to both switches.

  • Hi. This is on the "Low Quality Posts" list: "This answer was flagged as low-quality because of its length and content." Would you add a sentence or two? Thanks. Feb 5, 2020 at 12:28
  • Thank you for your answers, it was really nice to get help! just wanted to say that I did it, lol, I took off the switches, checked which wire was hot, it was red, so then I connected properly the switch and the timer, that I bought, the timer is Intermatic ST01, it doesn't require neutral, it has a battery. So all is well, thank you again for responding , that helped a lot. I studied these things long time ago and forgot, but now it is much more clear and it's actually simple, as long as you are careful to do according to proper instructions and follow safety rules. Thanks
    – user111959
    Feb 9, 2020 at 1:22

It sounds like the WHITE is the hot wire (common feeding both switches) and the BLACK and RED are the switch legs for the lights (loads). To find the HOT wire, test between the WHITE AND GROUND and see if you read 120 volts? If so, that is your hot wire. If there is no neutral in the box for the timer you will have to feed a new 2 wire HOT AND NEUTRAL in the box. Hope this helps.

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