I just replaced a light switch with a switch that has a dimmer on it. The lights I wanted to have on the dimmer are working fine, but the problem is with the other lights in the bathroom. The switch I replaced is in the hallway leading to the bathroom. The switch I replaced is now affecting the bathroom lights in an odd manner. The only way for me to turn the bathroom lights on now is to have those switches in the on position and then have the new hallway switch in the off position, yes the off position. If I have the hallway switch in the on position, which obviously turns the hallway lights on, it turns the bathroom lights off. The dimmer also works with the bathroom lights, but again the hallway switch has to be off for the bathroom lights to be on. So because of this I cannot have both the hallway and bathroom lights on at the same time. This is confusing me... any help is much appreciated.

Thank You!!

Are the hallway lights controlled by "3-way" switches? (Is there a switch at both ends of the hallway?)

I originallyf thought it was just a single pole switch as no other switches affect the hallway lights, but when I was taking the switch out I noticed that there were 4 wires plus the ground. So I bought a 3 way switch and connected it that way. This is the only switch that affects the hallway lights, but now for some reason the new hallway switch is affecting the bathroom lights, which it was not doing before.

How many terminals, not wires. If 4 terminals, then it could be a 4 way switch which are used in n-way circuits.

You could have mixed a wire up.

I'm sorry there were 3 wires plus the ground. On the old switch two of the wires were plugged into the back of the switch with the third wrapped around a screw on the side of the switch.

Another good way to identify a 3-way switch is there is no ON-OFF marking stamped into the toggle. You will also notice three wires connected to the switch. One of the screws will be a different color.
Three way switches are installed where a light needs to be controlled from two different points, such as the top and bottom of a stairwell, both ends of a hallway, or two entrances to a room.
There is also a 4-way switch, which is sometimes used to control a light from 3 or more locations. This is not very common.

I concur with K.I.S.S. You have a wire mixed up.

I know this doesn't help much now, but always make a diagram before you take apart any wires. We have a saying in the trade: Two wires, hook it up. Three wires, screw it up. Four wires, give it up.

I'm assuming you installed a dimmer in place of one of the 3-way switches, and I am also assuming you installed a 3-way dimmer.

Look at the terminals of the old switch. There should be one that is a different color. (It is usually on the side that has two terminals) The wire connected to this terminal is the common wire. When you install the new switch, this wire must be connected to the common terminal of the new switch.

Once you have figured out the common wire, it doesn't matter which wires go to the other terminals.

I have tried all combinations of wires and nothing seems to be working correctly. Is there a chance I have an incorrect type of switch?

Trying to visulise this, I bet you that out of these three wires:

One wire is volting incoming
One wire is voltage outgoing to the bathroom circuit
One wire is the switched wire leading to the hall way light.

When you hooked up the three way switch on the bathroom, understand what a three way switch is, it's a switch with two possible "outputs" and one input. Voltage in the "common" and then depending on how the switch is set, voltage will either go out of one terminal or the other.

This would explain why you have to have to have the hall light "off" for the bathroom light to work. When you flip the hall light, the contacts change, and the hall light comes on and the bath light goes out.

I may be way off base here, but it's the only logic I can get out of this without seeing it myself.

To test this, unhook all of the wires, get a voltage meter, and find out which wires are "hot".

If only one wire is hot, then chances are one one of the others goes to the hall light fixture, and the last one goes to the bathroom circuit.

If two wires are hot, then... I'm out.

IF this turns out to be the case: (if the above is NOT the case, DISREGARD the below statement)

Then you will need to discover which of the "not hot" wires goes to the bathroom, and which to the hall light. If it were me, I'd wire nut the hot with one of the wires, throw the breaker on and see which one lights. If it's the hall light, then mark that wire. If the bathroom, mark that one. Unhook the connection. Connect the hot wire to the bathroom light wire with a small pigtail for your dimmer. Then on the other wire leading from the dimmer, connect it to the hall light.

It would appear that you purchase the wrong dimmer switch and wired it incorrectly.

It appears that you had a single pole switch in the hall. One of the two wires connected to the back of the original switch was the hot . The other was the hot going to the bath light. The third wire that was under the screw was the switch leg going to the hall light.

Remove the dimmer switch. Since you probably don't know which wire is which,
Connect any two wires together with a wire nut (call them A & B). Turn the power on. If the bath light functions properly you have returned power to the bath. If the bath light does not function properly disconnect the two wires and connect A to the third wire (C). Turn power on and check again. If bath light does not function properly disconnect A & C, then connect C & B.

One of the three combinations will restore power to the bath.

Return the 3-way dimmer switch and purchase a single pole dimmer. Connect the two wires you have wire nutted together to one side of the dimmer and the remaining wire to the other side.

OK, lets ask this differently.

We know there were 3 wires and the ground.
There was 1 green screw on the old switch.

How many brass screws on the switch? 2, right?
With an ON/OFF marking on the switch itself, right?

If so, then remove the switch:

Wirenut two of the wires together. See if every thing else behaves properly. If not, try the other two combinations.
Watch out for things like lights at half brightness etc.

Now add the switch.

I'm suspecting a SPST switch where two wires were attached together: One with screws and one in the back to the same terminal.

Quote:

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I'm suspecting a SPST switch where two wires were attached together: One with screws and one in the back to the same terminal.

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I should have picked that up when the OP said two wires were inserted into the back of the switch and one wrapped around a screw. But I got hung up when he said it was a hallway. I thought 3-way's at either end.

I can see what happened:

1. The original wiring had a hot wire tapped into the line side of the 2-way switch. (Attached under the screw.)
2. OP replaced the 2-way in the hall with a 3-way:
-hot wire to the common
-switch leg for the hall light on one runner
-bathroom circuit on the other runner (Bathroom light in series.)

When the hall switch is in one position, the hall light works
When it is in the other position, the bathroom circuit is energized. Now the bathroom light will come on when the bathroom switch is is turned on. Turning the hall switch to the other position drops out power to the line side of the bathroom switch, so the bathroom light goes out. (It also threw me off track when the OP said he turned the hall switch OFF and the bathroom light operated by it's switch, since a 3-way switch has no ON/OFF markings)

Solution:

Get a pencil and paper.
Get a 2-way switch.
Turn off the breaker.
Remove the hallway switch and unwire it.
Turn the bathroom switch ON.
Wire nut two of the wires you removed from the switch together, cap off the third wire with a wirenut, turn the breaker on and see which light comes on.

NOTE: If we call the three wires A, B, and C, there are three ways you can connect them (A+B together, B+C together, and A+C together.)
One combination will operate the hall light, one combination will operate the bathrooom light, and the third combination neither of the lights will work.


Repeat until you find the combination for both lights.

Wire nut the two wires that work the bathrooom light together with a short "pigtail."
Connect the other end of the pigtail to one side of a 2-way switch.
Connect the remaining wire to the other side of the 2-way switch.

Next time you replace a device, remember to draw a diagram before you remove any wires.