One light switch in a 3 gang box trips the breaker every single time. This switch is for 3 exterior lights. All other switches and outlets on this breaker work fine.

We moved into this house about 10 months ago and this switch has been doing this from day 1. Our neighbor said the previous owners used to turn the lights on all the time.

I have tested the breaker and it reads 120V. I have replaced the switch and tried removing the bulbs but no improvement. The only time it doesn't trip is when I leave the first fixture on and remove the other 2.

So, I disconnected fixture 2, left the wire connected. Breaker still tripped. Disconnected the wires between 2 and 3 and left 1 and 2 connected. It tripped.

Breaker does not trip if only 1 and 2 are connected. I also tested fixtures 2 and 3 by connecting them to the second spot and they both worked. So, the fixtures are good. All the bulbs work as well.

Fixtures 2 and 3 are on both sides of my garage door. It seems the wires between 2 and 3 could be faulty. What is the best way to check if the wire is faulty or damaged without breaking the wall? It seems like the wire goes above the garage door.

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    How are you "removing the other two fixtures?" Are you disconnecting them from the circuit at the first fixture, or are you simply removing lightbulbs, or...? – ThreePhaseEel Oct 29 '19 at 23:18
  • Removing light bulbs did not make any changes. So, I removed the fixtures from the circuit one by one. Only one particular fixture does not trip the breaker. It seems like it is the first one in the circuit. – Rb01 Oct 29 '19 at 23:30
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    So you have cut the problem down either the wiring has a short or the fixture has a short, flood lamps that have blown filaments can cause this by the way if the heavy wires of the filiment short out, I have even seen this with 60w bulbs. – Ed Beal Oct 29 '19 at 23:33
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    @Rb01 yeah, can you try turning the breaker off, disconnecting the incoming wiring at the second fixture, reconnecting the outgoing wiring at the first fixture, and turning the breaker back on again? That will tell us if the fault's in fixture #2, or in the wiring between fixtures 1 and 2... – ThreePhaseEel Oct 29 '19 at 23:38
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    Electronic motion sensors use scr or triac electronics to turn the lights on off. The failure of these devices is almost always a short until the short is blown open , remove the 2nd fixture totally and jumper the wires to power the 3rd fixture if that works toss the 2nd motion sensor and replace and all will be well if not it is the third fixture, almost never wiring but could be you need to break it down again it is simple for a pro I would have had this figured out in less than a half hour but with your info in 10 minutes – Ed Beal Oct 30 '19 at 2:35

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