I am changing a wall switch to a dimmer. The wall switch I am replacing
controls two recessed light fixtures. I can seem to get the dimmer to
work. Two wire go the back of the switch with the load on the screw.
I have tried to but cannot get the dimmer to work. Any suggestions on what
I could be doing wrong.

 

There should be two wires that connected to the oldswitch. Connect those same two wires to the new dimmer switch.

 

I think what KM means is that more than two wires attached to the old switch. So KM, please tell us exactly what the situation was before you removed the old switch. How many cables, how many wires, and how was everything connected. Don't just describe the wire connected to the switch--describe everything in the box.

 

The switch in question has three black wires attached. One is attached to
the terminal screw on the side, the other two are attached at the rear
of the switch.

Thanks
KM

 

It sounds like the old switch has backstab connections, as well as the traditional screw terminals. If this is correct, then you need to remember (or hopefully you wrote it down) how the wires were attached. The wire attached to the screw terminal and the closes backstabbed wire need to be attached to the same wire on the dimmer. The other backstabbed wire needs to be attached to the other wire on the dimmer.

If you have no ide which wire is which, then you need to make some tests.

One of the wires coming into the switch is always hot. You then either have two wires, one to each light, or you have one wire which goes to the first light and onto the second light, with the other wire being a wire that goes on to another recepticle or light.

You will have to test which case you have. Label the wires A, B and C. Two at a time, connect the wires together. Connect the wires together with the power off, turn the power on, and look for the lights to work. By testing all three combinations (AB, AC, BC) you will learn the method of wiring.

The incoming power wire goes to one lead on the dimmer. The wire or wires going to the lights go on the other lead of the dimmer. If you have a wire going to another recepticle or light then connect it to the incoming power wire.

 

Your dimmer has two wires. Your switch box has three that were connected to the switch. If you remember exactly how the three wires were connected to the old switch, then Bob told you exactly what to do in his first paragraph.

Otherwise...

The method Bob suggest is fine, and if that works for you, go with it.

Another method is simple trial and error. Pick any two of the switch box wires and connect them to one of the two dimmer wires. Connect the third switch box wire to the other dimmer wire. One of three things will happen when you turn the power back on:

1. Everything will work fine. The light is controlled by the dimmer, and everything else is independent of it.
2. The light will be on regardless of whether or not the dimmer is, and something you don't want to be controlled by the dimmer will be controlled by the dimmer.
3. The light will be controlled by the dimmer, but so will something else too that you don't want to be controlled by the dimmer.

If you don't get #1, then pick two different switch-box wires to connect to the same dimmer wire. There are only three possibilities, so it won't take long to get it right.

 

Is this the only switch that controls the lights in question? If there is another switch which would turn the lights off and on, then you have a three way switch, which explains the three wires on the switch.

 

I was just going to suggest that, but it's interesting that it's three black wires and not black/white/red, or even black/white/black (if a second cable is used for the traveler).

Dimmers are now built so they can be placed in a three way circuit as an option. Instructions generally tell you to wire nut the extra wire, and even include a wire nut to use if you're using it as a simple switch. Otherwise it operates as your 3rd wire traveler...

 

Well guys I have tried wiring the switch as suggested and I come up with
the same result. The lights come on when I put the power back on but
the dimmer does nothing. I tried to shut the lights off but no result, I tried
to dim the lights and again nothing. As far as I can see the only switch that
controls these two lights is the one I am trying to change.

Must the switch be grounded in order for the it to work. That is the only
wire I havent connected. I also wired the switch according to the instructions
that came with the dimmer. I also have tried a different dimmer thinking I may
have gotten a bad one.

Same results all the way around.


Thanks
km

 

Leave the dimmer out of the operation and determine what the three wires are for. Then we can worry about the dimmer.

 

First thank you all for your patience. I could not have finished
without your help. The dimmer is working fine and all is well in
the household again. Again I appreciate all of your help

km