3-way switch, always hot

[John Smith]

I just bought a 3-way switch. I notice that when hot wire is connected to the black screw, both traveler wires are always hot no matter how I flip the switch (the hot wire coming out of the other 3-way switch is always hot, not responding to the position of this switch).

I measured the voltage across the black and either of the two traveler screws and it was 0. However, if I measure the resistance, it does seem to work (0 between the black and one of the traveler screws and infinite if the switch is flipped. Same for both traveler screws.)

This doesn't make sense, does it?

[John Grabowski]

Throw away your meter and hook up a light bulb to the circuit instead. Then report back here.

[RBM]

I love it!!! One would tend to believe the consummate professional would advocate only the newest, most technically advanced test equipment is adequate to properly diagnose these problems... and what does he recommend? "Scrap the freaking meter, and get a light bulb" Works for me

>

[RLM]

[RLM]

You might want to bookmark these.

[terry]

Agree use a lamp! He's either picking up induced voltage from adjacent 'live' wires, or capacitance coupling through switch? Cos even cheap meters are sufficiently sensitive to do so; OR there is potential coming back on the 'other' wire from the other 'switch' of the two switches used in a so called '3 way switch' set up. PS. Why do we call it '3 way'? Maybe cos of the usually three wires between the two switches (compared to the usual two for a non-3 way set up)? OR ........ ? Mostly it's a two switch arrangement; typically one switch at top and another at bottom of stairs! Although there is a special 3rd switch available (although never seen one) that swaps over the two carriers of a double pole switch to allow use of witches in three locations.

[metspitzer]

You didn't say if the switches ever worked.

If you just bought a new switch, the chances the new one is bad are low.

It sounds like the wiring from the other switch may be the one that is wrong.

If the switches were working properly before you "fixed" them, then what I would do is take both switches off and locate the hot. (only one of the 6 should be hot.

I would then put the new switch at that spot and check the other side.

Take your tester to the other point and see if the new switch makes two of the wires hot by switching back and forth. The wire that doesn't go hot should be the common.

Reminder: Always turn the power off before making any wiring changes.

A good 3 way will have 0 ohms between the common one traveler in one position, and infinite ohms between the common to the other traveler. When you flip the switch you should have the reverse.

[RBM]

Agree use a lamp! He's either picking up induced voltage from adjacent 'live' wires, or capacitance coupling through switch? Cos even cheap meters are sufficiently sensitive to do so; OR there is potential coming back on the 'other' wire from the other 'switch' of the two switches used in a so called '3 way switch' set up. PS. Why do we call it '3 way'? Maybe cos of the usually three wires between the two switches (compared to the usual two for a non-3 way set up)? OR ........ ? Mostly it's a two switch arrangement; typically one switch at top and another at bottom of stairs! Although there is a special 3rd switch available (although never seen one) that swaps over the two carriers of a double pole switch to allow use of witches in three locations.

You never use 3way witches in three locations. You must use at least one warlock(4way) between the two witches

[Oren]

It's written on the box? :-/

[Wayne Whitney]

This is to be expected, as there should be no voltage drop across a switch, since there is no load.

This suggests the switch is fine and you have miswired the circuit.

Cheers, Wayne

[Jeff Wisnia]

Assuming both switches are in good shape, and the wiring is correct, an explanation would be that the two traveler wires have somehow gotten shorted to each other.

Jeff