3 way switch problem.

joed · 12-30-2009, 05:46 PM

The drawing is not representing what you have or the breaker would not be tripping unless the cable between sw1 and sw2 is damaged.

do this test for me. Disconnect the black and white from cable a at sw1 and cap the ends off separately. Trun power back on and measure the voltage on sw 2. Tell me what you are using to measure the voltage. A digital meter might give false readings.

At any point in this testing does the light go on.

Blade_316 · 12-30-2009, 06:40 PM

Quote:

Originally Posted by joed

The drawing is not representing what you have or the breaker would not be tripping unless the cable between sw1 and sw2 is damaged.

do this test for me. Disconnect the black and white from cable a at sw1 and cap the ends off separately. Trun power back on and measure the voltage on sw 2. Tell me what you are using to measure the voltage. A digital meter might give false readings.

At any point in this testing does the light go on.

Quote:

Originally Posted by joed

The drawing is not representing what you have or the breaker would not be tripping unless the cable between sw1 and sw2 is damaged.

do this test for me. Disconnect the black and white from cable a at sw1 and cap the ends off separately. Trun power back on and measure the voltage on sw 2. Tell me what you are using to measure the voltage. A digital meter might give false readings.

At any point in this testing does the light go on.

B & W disconnected in SW1

SW2 no power whatsoever
SW1 no power whatsoever
No lights

B & W connected in SW1(down) SW2(up)

SW1 B & R(top) 120v
SW1 B & R(common) -
SW1 R & R 120v
SW2 R & W 120v
SW2 R & B(common) 120v
SW2 B & W -

B & W connected in SW1(up) SW2(up)

SW1 B & R(top) 120v
SW1 B & R(common) 120v
SW1 R & R -
SW2 R & W 120v
SW2 R & B(common) 120v
SW2 B & W -

B & W connected in SW1(down) SW2(down)

SW1 B & R(top) -
SW1 B & R(common) -
SW1 R & R -
SW2 R & W 120v
SW2 R & B(common) -
SW2 B & W 120v

B & W connected in SW1(up) SW2(down)

SW1 B & R(top) -
SW1 B & R(common) -
SW1 R & R -
SW2 R & W 120v
SW2 R & B(common) -
SW2 B & W 120v

Using digital multimeter.

I hope you can decipher this code

oberkc · 12-30-2009, 07:38 PM

I think I understand the code. I think, also, that I am not smart enough to reach conclusions other than continued suspicion that your wiring is not as it seems. Some of the voltages you report don't seem possible to me, based on the wiring diagram.

In your second scenerio "B & W connected in SW1(down) SW2(up)" voltages you report imply red (common) and black of switch 1 and white and black of switch 2 are connected by the switch. If so, the red wire travelling between the switches in unconnected to anything, anywhere. It is not grounded. It is not connected to the supply. It is not in the electrical path at all. How can there, then, be a voltage between it and anything? Makes no sense to me. (By the way, you did not specify whether you performed these tests with bulb in place, and whether it was on or off in your various scenerio. That may help.

If it were me troubleshooting, I would remove all fixtures and switches, leaving all wires unconnected. I would be verifying voltage at the wire in the light box (and only the light box), including proper polarity? I would be checking for continuity between conductors within each wire bundle (should be none). I would check each switch (by measuring continuity between connectors in varying switch positions), to be sure the connection known as common is, in fact, the common. I would be measuring continuity between wires in the various boxes to verify wiring diagram. I would be measuring continuity between each conductor and known ground, to ensure there is no unexpected shorts somewhere.

I continue to believe the wiring diagram would be correct if the black and white wire of switch 2 were exchanged. The fact that exchnging these wires causes trouble makes me believe that the actual wiring is inconsistent with the diagram, or that there is some short somewhere.

I look forward to learning along with you from the posts of others. Sorry I could not help more from all the effort you have put in so far.

Blade_316 · 12-30-2009, 08:54 PM

SW1(down) SW2(up) is the only situation where the light is [ON]

joed · 12-30-2009, 09:25 PM

New test.
Remove the two switches so that the cable between has all three wires disconnected from everything.
With power off.
Use the ohm scale and measure between each wire and the other wires and between each wire and the ground wire. It should be open all around.
Then short two wires together at one and see if they measure shorted at the other end.

Blade_316 · 12-31-2009, 09:25 AM

Quote:

Originally Posted by joed

New test.
Remove the two switches so that the cable between has all three wires disconnected from everything.
With power off.
Use the ohm scale and measure between each wire and the other wires and between each wire and the ground wire. It should be open all around.
Then short two wires together at one and see if they measure shorted at the other end.

Ok, here goes...
Both switches removed - Continuity check:

SW1 (Box/ground) = SW2 (Box/ground)
SW1 (Red cable C) = SW1 (Box/ground)
SW2 (Red) = SW2 (Box/ground)
SW1 (Red cable C) = SW2 (Red)
SW1 (Black) = SW2 (Black)

Switches removed - shorted wires on SW1:

SW1 (Red & Red) = nothing on SW2 (other than red and box)
SW1 (Red cable A & Black) = nothing on SW2 (other than red and box)
SW1 (Red cable C & Black) = SW2 (Red & Black) / SW2 (Black & ground)

Switches removed - shorted wires on SW2:

SW2 (Red & White) = nothing on SW1 (other that red cable c and box)
SW2 (White & Black) = nothing on SW1 (other that red cable c and box)
SW2 (Red & Black) = SW1 (Red cable C & Black) / SW1 (Black & ground)

Is it normal that red and box are linked?

oberkc · 12-31-2009, 10:02 AM

I am having to respond without access to your diagram. Hopefully, I remember it well enough.

Are you saying that your red wire between switch 1 and 2 is measuring no resistance between it and ground!? Does this sound normal to you? It sure does not sound normal to me. There is nothing in your diagram which would explain why there would be a path to ground in this red wire, expecially with both switches disconnected. It sounds to me as though you have found your problem.

Until I get a chance to again look at the diagram, I would be trying to identify why there is this short. Is your wiring accessible? Is it old enough to suspect failure as a plausible explanation? Did someone drive a screw through a wire somewhere?

Did you remove separate all the grounds when you performed this test? It sounds like you may have left them on. Try separating all the grounds and see if you still have this problem. If this solves the problem, I would take that as confirmation that you have short between ground and red in the wire between switch one and two.

joed · 12-31-2009, 10:07 AM

Quote:

SW1 (Red cable C) = SW1 (Box/ground)
SW2 (Red) = SW2 (Box/ground)

Are you saying the red cable measures connected to the ground?

Quote:

Switches removed - shorted wires on SW2:

SW2 (Red & White) = nothing on SW1 (other that red cable c and box)
SW2 (White & Black) = nothing on SW1 (other that red cable c and box)
SW2 (Red & Black) = SW1 (Red cable C & Black) / SW1 (Black & ground)

This would seem to indicate the cable you think run sw1 to sw 2 does not. When you short red/white at sw2 it should measure shorted at the other end. It would also explain why the breaker is tripping on certain hookups of sw2.

You need to determine for sure where the cable run. Then we can help you.

Blade_316 · 12-31-2009, 01:22 PM

Alright, here's the deal.

Cable C is shorted on RED and BareGround, I don't know where, I went up to the attic and didn't find any fault. So I bought a new cable tested it by just running in across the room. It works like a charm (switching B & W in SW2).

So now I just need to fish the new wire and I'm all set. Any tips on fishing this wire?

Thanks again for all the help, this switch has been bugging me for the last year.

oberkc · 12-31-2009, 01:32 PM

Congratulations on a successful troubleshoot.

Methods vary, depending on access. Do you have access above or below? Are any of the walls insulated? How is the cable secured at each entry to the box? Plastic or metal?

Blade_316 · 12-31-2009, 01:42 PM

Quote:

Originally Posted by oberkc

Congratulations on a successful troubleshoot.

Methods vary, depending on access. Do you have access above or below? Are any of the walls insulated? How is the cable secured at each entry to the box? Plastic or metal?

I have access above where the faulty wire travels. One of the walls is insulated, I don't know if the wire is secured within the wall...

If I split the wire in two, one half should be good. Could I place a junction box and only have to fish one switch? The junction box would be in the attic/crawlspace.

oberkc · 12-31-2009, 02:07 PM

Great minds think alike! It sounds like you will have it relatively easy. Yes, I was going to suggest cutting the faulty wire near both walls, then measuring resistance between red and ground on both ends. Hopefully, the fault was in the section removed, and you could join with junction boxes and new wire. Perhaps, instead, first cut in the middle and identify which half is faulty, then focus on that side.

Yes, I would expect that the cable is attached in the wall (I believe this is code). If you found that the short was in the wall, then you will have to find a way to snake it down. You may need to drill another hole in the wall top plate through which to feed the new cable. Be sure to fill with silicone to make a fire and draft break.

Can you loosen the strain relief from the inside of the box? Hopefully so. I would push any faulty wire into the stud bay and use that opening and strain releif for the new cable.

As for getting the wire from the box to the top plate, a wire snake is the only method I can think without cutting a hole in the wall. If you have enough manuvering room overhead, perhaps a tent pole, or somethine rigid like that would be a good option. It will be a bit trick locating the far end of the pole or snake, but a little patience and ingenuity should suffice.

Depending on wall construction and finish, it may actually be easier to cut a couple of strategically-located access holes in the wall. If it is simple drywall and paint, a repair of the access holes might be the easiest method.

Hopefully, those with direct knowledge of code could offer other considerations, esp need to secure new wire and fire break.

Blade_316 · 12-31-2009, 02:20 PM

Yeah, I'm going to cut a few holes, it'll probably save me a lot of frustration.

Drywall and paint seems easier

.

Was having this short a fire hazard waiting to happen?

oberkc · 12-31-2009, 02:38 PM

Given that the way it was originally miswire (still going by memory) and the fact that you were not throwing breakers, I would assume that the red wire was never actually energized. I would say, then, that this was not a hazard as wired originally. Only when you tried to wire the circuit correctly did you notice problems and create potential fire hazards.

On the other hand, if you have a spouse that needs this as justification for doing this work, then, "sure, it is a safety hazard". That is my story and I am sticking to it.

joed · 12-31-2009, 04:02 PM

Remove the boxes. Then you have big hole to fish the wire. One side of the box is probably a stud. A sawsall or one of those hacksaw blade holders that leaves half the blade sticking out like a sawsall, will slice through any fastener holding it on. Loosen the clamps and you should be able to work it out or even in. If they are plastic just smash them.

The problem with the cable could be right at one of the clamps if someone tighten them down with full force.

cable if fairly stiff. If you can gain access direct above the switch then you should be able to fish it down.

You could replace only half the wire if you wish.