How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask AssuredElectrical Your Own Question
AssuredElectrical, Master Electrician
Category: Electrical
Satisfied Customers: 4241
Experience:  Contractor-42+ Years in the ElectricalTrade
Type Your Electrical Question Here...
AssuredElectrical is online now
A new question is answered every 9 seconds

My problem: I replaced a light light switch - 1 Black wire

Customer Question

My problem: I replaced a light light switch - 1 Black wire connected to the common/black screw, the 2 travel wires connected across from each other, electrical runs in series Bathroom section A has one light switch, Bathroom section B has a second light switch and exhaust fan on double switch plate. When I flip the switch to turn on the light in bathroom A, it turns on, when I turn the light off in bathroom A it turns the light and fan on in bathroom B. I can turn both switches off for bathroom A and B and both are off. How do I fix this alternating power problem?
Submitted: 1 year ago.
Category: Electrical
Expert:  AssuredElectrical replied 1 year ago.

Welcome. My name is ***** ***** would be glad to assist.

I have read the information, and based on the situation, it appears that one wire for switch A is connected to the switch B since switch B can change the state of switch A

Since A only has one switch on the light, there are only 2 screws on the switch, one is power and the other is the wire to the light.

These 2 black wires will be from 2 different cables.

The switch on B having 3 screws of course, is your 3 way setup.

On the 3 ways, one 3 way gets power on the Black screw

The other 3 way gets the light wire connected to the black screw

Then the 2 brass screws have the traveler wires in no particular order connected which is how the 3 ways flip flop the power to the light.

That is the key.

So, somehow you have power to the switch A it seems, since you can turn the light off with B.

Verify the wires int he box, the 3 ways should have a common cable with the travelers, usually a 3 wire cable of which 2 are used between the switches, so you can check the switch that was not changed to find those 2 wires and put on the brass screws.

Let me know how it progresses


Customer: replied 1 year ago.
Did not help. Hired an eletrician and found out it was not 3 day.
Customer: replied 1 year ago.
Not 3 way.
Expert:  AssuredElectrical replied 1 year ago.


Your information was the switches were 3 ways, so someone can only provide details and information from what you, yourself post for us to use.

You posted this:

"1 Black wire connected to the common/black screw, the 2 travel wires connected across from each other"

That is a 3 way switch.

Would have been glad to provide other information if the details would have been provided and posted . We can only work with what you provide as the existing