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The bathroom has a light/fan mounted in the ceiling. The upper switch controls the light and the lower switch controls the fan.

The upper (light) switch needs to be wiggled and held in place to operate. As this is very annoying, I decided to replace the double switch.

I bought a new switch and wired it EXACTLY like the old one - red wire to upper right, black wire to lower right, white wire to upper left and bare wire to the ground screw.

The upper switch now controls the light AND the fan, while the lower switch does nothing.

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    Can you post a photo of the wiring? – ThreePhaseEel May 18 '18 at 11:42
  • The camera on my phone is not working, but I will try to borrow one and post some photos... – user85910 May 18 '18 at 15:24
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    What got you in trouble was thinking about position (upper right, etc.) -- those are not standardized from switch to switch. Permanently abandon that way of thinking as it will get you in even worse trouble with GFCIs, 3-way switches etc. You need to go by functions of the wires/screws (designated by labeling or color, brass, silver, black, etc.) – Harper May 18 '18 at 17:11
  • The camera on my phone is not working, but I will try to borrow one... He never posted the pics - the buttons on the borrowed camera were not in the same place as his own. – A. I. Breveleri May 23 '18 at 14:26
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The relative locations (upper right etc) of the terminals on the switch are not the factor with which you should be concerned. You need to know which terminal is the common. That gets the AC from the circuit breaker. The other two go to the loads. Are they marked? Do you have an ohm meter?


edit:

OK, based on your comment I think I know what's happened.

Your old switch appeared to you to have three terminals, but most likely it really had four, but two of them are connected together - maybe internally, hidden from you, or perhaps simply unnoticed? The new switch probably has an external shorting strap/bar - the RED in the pic below - connecting the two commons together.


                         enter image description here




The switches you've been using are both set up as a pair of single-pole single-throw switches.

Previously you had the AC coming in on the Common terminal(s) and the two loads (fan and light) each getting one of the Load terminals. That worked as desired.

When you replaced the switch, you wired the AC coming in to one of the terminals on the Load side (A1 or B1), and wired your loads to a Common terminal. Since the common side is shorted together, when you turned on the one switch to which you wired the AC input power, both loads powered up. The other switch is effectively non-functional.

  • I'm not sure if the old switch has marked terminals (I put it back in when I couldn't get the new one to work. The new switch has two black screws on the right side (each marked "common") and two lighter-colored screws on the left side (the upper marked A1 & the lower marked B1). – user85910 May 18 '18 at 4:24

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