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Old 05-15-2012, 10:56 AM   #1
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Finding the hot


This may sound like a daft question but how do I find the hot in an old 3 way gang switch. It has been faulty ever since I moved into this house ( you can only switch it on from upstairs or vice-versa). I changed the switches and rewired according to what I found which obviously changed nothing. There is no ground as these wires are OLD and no metal box. I am using a multimeter but get no reading from any of the wires in either the box upstairs or the one downstairs. I tried touching the other end to a piece of copper wire with still no joy. I have tested the multimeter on different live outlets and it works. Do I need a different multimeter or something else to test with? I found someone talking about measuring resistance but this multimeter only has DCV DCA ACV and B TEST. Thanks again for helping me out!

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Old 05-15-2012, 11:00 AM   #2
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Finding the hot


Quote:
Originally Posted by Finnmaccool
This may sound like a daft question but how do I find the hot in an old 3 way gang switch. It has been faulty ever since I moved into this house ( you can only switch it on from upstairs or vice-versa). I changed the switches and rewired according to what I found which obviously changed nothing. There is no ground as these wires are OLD and no metal box. I am using a multimeter but get no reading from any of the wires in either the box upstairs or the one downstairs. I tried touching the other end to a piece of copper wire with still no joy. I have tested the multimeter on different live outlets and it works. Do I need a different multimeter or something else to test with? I found someone talking about measuring resistance but this multimeter only has DCV DCA ACV and B TEST. Thanks again for helping me out!
Try one of those voltage pens.

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Old 05-15-2012, 11:18 AM   #3
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Finding the hot


With your meter, you need a ground or a neutral to test for the hot. From what you said, I'm guessing your receptacles are two wire, with no ground.

If the receptacles have the wider slot for the neutral, you could take an extension cord, plug it into a nearby outlet and use the neutral slot in the extension cord to test for your hot at the switch. If you have three wire receptacles, I would suggest using the ground on the extension cord.

But it would be a lot easier to buy a tick tester and use that.
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Old 05-15-2012, 11:39 AM   #4
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Finding the hot


Does your meter read continuity? You gotta setting that says ohms or has a capital omega symbol?
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Old 05-15-2012, 01:14 PM   #5
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Finding the hot


So I just tried a voltage pen and I get a continuous red and beeping from 1 of the 3 wires in the downstairs box and from the other 2 it beeps for a few seconds and then stops then restarts and stops. I am guessing the continuous one is the hot and should be the common wire for the 3 way! As for the upstairs box, not a peep from any of the 3 wires. Remember this is old wiring so I have no colours or a grounded box to test from.
To answer the question regarding the multimeter, yes there is a kind of red circular switch above where the probes exit marked OHM but on the main multimeter turn wheel, there is no resistance option. I have attached a photo of the multimeter and the new pen I have. So my next question is: How do I find the common wire for the upstairs box (supposing that I have just located the one in the downstairs box?) There are 3 wires here and 2 must be the travellers.
I like the idea of using a grounded extension cord but alas the only ones I have are 2 wire versions as this was an old house with 2 hole sockets. Thanks for that idea though.
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Old 05-15-2012, 01:46 PM   #6
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Finding the hot


1. Turn the power off.

2. Use a wirenut to connect any two wires in box (A).

3. Set meter dial Rx100.

4. Go to box (B), test all combinations of wires and see if needle jumps to between the two extremes. All the way left or right.

5. If not, try another pair and repeat until you do.

6. When you find the correct pair, these are the travelers.

7. The third wire in each box goes on the common, black screw, and the the pair on the brass screw.

8. Report back
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Old 05-15-2012, 02:15 PM   #7
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Finding the hot


OK thanks for your info. Just to be clear, there are 3 variations on how the 3 wires in box A can be connected as you suggest. I tried all 3 just now and went upstairs to test box B with each change. I put the 2 probes on the different wires in their variations in box B with NO movement of the needle. I just checked the multimeter in a socket and it moves to the left when set to RX100 setting. Just double-checked so am I being dim or do I need to be connecting wires in box B too?
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Old 05-15-2012, 02:32 PM   #8
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it sounds as though the switch downstairs is wired wrong... the constant HOT wire should go to the common terminal (brass coloured) on your 3-way switch. the other two wires (connected to the black terminals) are the feeds to the upstairs switch. depending on which position the switch is in determines which wire carries the voltage. upstairs the switch is wired the same, except that the light (or load) is connected to the common terminal...
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Old 05-15-2012, 03:23 PM   #9
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Yes indeed but that does not solve the problem of which wire is which.
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Old 05-15-2012, 03:48 PM   #10
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Quote:
Originally Posted by Finnmaccool View Post
Yes indeed but that does not solve the problem of which wire is which.
1.Testing voltage with meter set on ohms possibly just fried it. I never said do that.

2. I said if one pair does not do anything, repeat with other two combos.

Aargh, you are supposed to switch wires in (A) and repeat tests at (B).

Touch your 2 probes leads together. What happens?

Last edited by Code05; 05-15-2012 at 03:51 PM.
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Old 05-15-2012, 03:55 PM   #11
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The meter is working still - can you look at the pic of the meter please? How could I set it to ohms? I have it set to RX100 as you said. I have no idea what this means anyway. All 3 pairs have no effect on the meter needle which is why I am wondering if I am still doing something wrong.
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Old 05-15-2012, 04:04 PM   #12
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Sorry now I understand- RX100 is for measuring resistance. In the immortal words of a famous American - doh! However this still gives no help as I get no measure of resistance from these bloody wires. Should it be set lower?
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Old 05-15-2012, 04:06 PM   #13
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Finding the hot


by setting the meter to RX100, you HAVE set it to Ohms. R=resistance, X=times and 100=100xmeter reading..

can you take a couple of pictures of the upstairs and downstairs switches with them pulled out... identify which of the wires downstairs is live all the time.. and which terminal on the switch it is connected to..

someone once said, a picture is worth a 1000 words....
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Old 05-15-2012, 04:24 PM   #14
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Finding the hot


Quote:
Originally Posted by Finnmaccool View Post
Sorry now I understand- RX100 is for measuring resistance. In the immortal words of a famous American - doh! However this still gives no help as I get no measure of resistance from these bloody wires. Should it be set lower?
Yes, I just started there cause I am lazy and with such a small resistance I picked that setting.

Let me be clear, in box (A) you have 3 wires 1,2,3.

With 1 and 2, then 2 and 3, then 3 and 1 wirenutted together, and testing each set at (B) you should get a reading.

If not repeat tests at Rx10, then Rx1.

Does this make sense?

Power is off, correct?

And both switches are removed?

Last edited by Code05; 05-15-2012 at 04:28 PM.
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Old 05-15-2012, 04:37 PM   #15
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Finding the hot


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Originally Posted by Finnmaccool View Post
Yes indeed but that does not solve the problem of which wire is which.
you already found the HOT wire. it is the one that is constantly hot in the switch box downstairs..

the HOT and the other wires are connected wrong, so as per previous suggestion, pictures and identify each of the wires...

you should have a 3-wire between downstairs and upstairs. the 3-wire will have a black, red, white, and a bare ground conductor... do you have those??

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