advice on a single pole light switch - 3 black wires in the box


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Old 11-18-17, 05:08 PM
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advice on a single pole light switch - 3 black wires in the box

Hello,

I am having troubles replacing a light switch as it does not turn on after replacing the single pole switch. After turning the power of I opened up my box and i could see 3 black wires. 2 of the wires are connected via wire nut and then connected to the bottom pole. The third black wire is connected to the top pole. when I reconnect these to the new switch, I see some unexpected behavior. That is when I check the connection with the switch off, the meter reads 120V, however when I turn the switch on the Voltage drops to near zero and the light does not turn on. I did try to swap the poles for the wires, however I see the same behavior. Please let me know if you have any thoughts.

Thanks!
 
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Old 11-18-17, 05:28 PM
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Last edited by Norm201; 11-18-17 at 05:29 PM. Reason: graphic not loading
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Old 11-18-17, 05:44 PM
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Norm, I will attach a couple of photos when I get a chance. Two of the black wires are connected together along with a third wire (the third wire's purpose is to connect the connected pair of black wires to the switch). There is another black wire on the top pole of the switch.
 
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Old 11-18-17, 06:29 PM
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Welcome to the forums.

It is very common to see two wires spliced with a short tail to go to the switch. This is the preferred method. That tail can go on either side of the switch and the remaining other wire can go on the other side.

If you use a voltmeter on the switch when it's off..... you will measure 120v between the screws as the switch is open. When you turn the switch on.... the two wires are shorted together and you will read 0v.

It sounds like you need to check for 120vac at your light or fixture.
 
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Old 11-18-17, 06:42 PM
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Pete, you are absolutely correct, I would not be surprised if the wires leading to the fixture or the fixture are faulty. The reason for the change out of the switch is the light was not staying on consistently when the switch was in the on position. I with start with confirming the original switch to see if if was or was not faulty, then I will move on to the fixture status.
 
 

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