Electrical – Replaced light fixture, now 3 way switch doesn’t work

electricalmultiway-switch

I replaced an old lighting fixture with a remodel can and led trim, but in doing so the three way switches no longer work.

I didn’t touch either switch’s wiring, but now the switch with the circuit running to it has to be on for the other switch to function. If the first is on, the other switch can turn on and off the light, but if the first one is off, the second switch doesn’t work.

My next step is to pull out the switches and check the wiring, but I’m curious if replacing the light could have affected the switches somehow?

EDIT: now with photos

first switch box

first switch back

second switch box

second switch back

Best Answer

Sometimes a NM cable is not fastened down along its length, either because it was fished through an existing wall (old work) or because the builder just laid it between the attic joists (poor work).

If the NM cable that you moved is not thoroughly fastened down, and if the strain relief at the other end is inadequate, then you probably moved the wires or wire nuts around inside the box at the other end and knocked one of the travelers off its terminal.

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