3 way switch problem... short?

[Integraoligist]

Hey all,
I have an odd situation in my garage.

I have 1 switch on both side of the garage turning the lights on/off.

One of the switches is old and it busted off… so I went and bought a new 3-way switch.

Installed the switch and everything was working properly for a week… then at 4 am in the morning all the lights in the garage turned on. So I got up and flipped the switch, they still stayed on… so I went to the other switch and flipped it, and again, it stays on!

So no I’ve got constant power going to the lights… I have to pull the fuse to turn them off.

I took out the new switch and tested it with my DMM, it works fine… so I wired it back up and test the V, and I’m getting about 14V on both sides of the switch! I test the continuity, one side of the switch is constant, and the other is speratic beeping… so I flip the switch and test again… same thing, one sides constant and the other is speratic.

Should I assume there is a short somewhere in this old Wiring? And if so, how did it all of a sudden happen while the lights were OFF and a week after it’s been running fine?

Thanks all for the help!

[HayZee518]

your three way switch is either switching the hot wire or the return to your load through two travelers. the newer three way switches have an odd colored screw - this is the switching side, the two brass screws are the travelers between the two - three ways. why your circuit would turn itself on is a mystery unless the three way you are using is a mercury quiet switch. On the yoke is stamped the word UP. this is the way it should be installed with the word up - UP! the mercury button inside the switch has two small holes in the ceramic with mercury bridging the contacts.
People always assume there is a short when things don't work right. A short is a condition when the hot doesn't make it to the load and then therefore blows a fuse or a circuit breaker. if the hot doesn't make it to the load and it doesn't blow the breaker or fuse then it is called an OPEN - NOT a short. Hope this straightens out the nomenclature part at least!

[Integraoligist]

it's not a mercury switch, just a regular 3-way... the colored screw says COMMON on it... so when I initialy put it togeather, i tested the bare wires to see which was the common, worked fine for that week....

tonight i took the new switch out totaly and just the the wires hang, while i went to the other switch and flipped her on/off... and it's still constent power to the lights.

i'm guessing is the "other" swich, and not the new one that has a problem now?

Thanks!

[HayZee518]

I always change both switches when somebody has a turn on the light problem from two places installation. [three way switches] I wish I could figure out why they call it a three way switch. the common screw is common to both sides of the switching mechanism in side. one side is open, one side is closed. depending on the position of the toggle.

[HayZee518]

3 Way Switching

Follow this diagram - it'll give you an idea how the circuit is supposed to work.