Wiring for light switch and exhaust fan

Question

Let me start by saying I don't really know what I am talking about, so my vocabulary may be incorrect. This is all based upon my best interpretation of the problem.

I am replacing some old light switches throughout my house. Each of the three bathrooms have an exhaust fan and lights that are on separate switches in the same box. In two of the bathrooms, there is a separate ground and hot wire for each switch. In the third, which seems to always have the most issues, I opened to box and I only see one ground and I believe only one hot. There appear to be separate wires leaving the box for the light and exhaust fan. It also looks like there is a wire that is only connected between the two switches. My guess is that this is because there is no hot wire for the other switch, but I'm not really sure. All of the wires appear to be attached using the terminals, with the exception of the wire between the switches which uses the push ins in the back.

I would like to replace the switches, but have no idea how I should wire them. Also, is this wiring setup the reason this bathroom has issues with switches/lights? Any help would be greatly appreciated.

Answer 1

The problem may well be the "push ins", aka "backstabs".

Ignoring grounds (green or bare, all go together), you have:

• Hot to switch 1
• Jumper hot from switch 1 to 2
• Switched hot 1 (light)
• Switched hot 2 (fan)

Rewire as follows:

• Take hot to switch 1 and connect two short pieces of black (or any color but white, gray, green or bare) wire and connect them with a wire nut.
• One of the short pieces goes to the "hot" screw terminal on switch 1
• One of the short pieces goes to the "hot" screw terminal on switch 2
• Switched hots are connected as before, but make sure to use screw terminals.

And if you are putting in new smart switches/dimmers (don't use a dimmer on a fan), motion sensors or anything else "special" that needs a neutral, you can add a short white wire to the bundle of whites in the wire nut. Replace with a larger wire nut if necessary. The other end goes to the "neutral" screw terminal on the switch.

Answer 2

Color code

First thing let's do is make this wiring clear. They sell 5-packs of multi-colored electrical tape for $4, and I'd like you to mark two wires like this:

At this point, something not normally true is now true: wires are color coded by function. Red is switched-hot to light or fan. Blue is switched-hot to the other one. Blacks are hots, whites are neutrals, and bare is equipment safety ground. Disregarding the drywaller's work, of course!

Deal with the backstabs

Backstabs are bad news. They cause reliability problems for everybody - not least, because they rely on a spring connection that costs a penny, and are buried in the guts where they cannot be inspected. Even these are done badly. The shanks of bare wire sticking up are flat illegal (they couldn't even bother looking at the cut gauge that plainly says how long to cut them).

Screw connections are better, but the leftside example is the wrong way to do them. They should look like on the right, with the wire entering from the back, no bare wire beyond the back face, all the wire under the screw stripped bare, loop 180° (better: 210°) around the screw. And be torqued to spec (usual error: too loose).

Pigtail, and you're done

Topology-wise, you see a wire nut already in use; a simple way to do the switches is to get more wire-nuts and use pigtails: short lengths of wire. You already have a black pigtail in the box. These can be had by buying wire by-the-foot at the store; you can get 2 pigtails per 1 foot. For a "universal-donor" pigtail, get 12 AWG and for a novice, get solid. (I use

On the bench, on each new switch, attach 1 black wire to the bottom screw, and 1 bare wire to the ground screw. Take them to the box and join

• All bare wires to each other with a wire-nut (best: red or green* nut)
• All black wires to each other with a wire nut (best: red or yellow)
• The blue wire to an open switch screw
• The red wire to an open switch screw

Again: this works because we color-coded the wires in step 1.

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* Nut colors indicate size. Except: green and tan are the same size as a red nut.