Hi,
I am replacing the old switch with a new one. The old one was a dimmer, but would control the light and the fan at the same time, so if you dimmed the lights, the fan speed would lessen.

I purchased a Lutron Skylark switch to turn on/off the light and control the speed of the fan. It is a dual outlet box. There are two sets of wires, one set from the bottom left and one from the top. Each set in the outlet box has a black, white, red, and a bare copper ground.

The control has a red, black, yellow, and green (ground). I have replaced dozens of these lights over the years and have never had a problem. I have tried several combination, but it either trips the reset or does not work at all. My thought was - black-black, red-red, ground-ground, and yellow-white.

Also, when I try to put the old switch back on, I cannot get it to work. I know it is getting power to the box though. Any help you could give me would be greatly appreciated.

Thanks!

How was the old switch wired?

How is the fan wired at the ceiling? This is a critical bit of information.

The yellow-white connection should have never been made may have fried your new switch.

How was the old dimmer wired?
From the cables in the box, what wires were connected to what?

OK, I took the fan off... the fan had a remote (which would be nice to keep, but not necessary). The remote had two wires, black (AC IN L) and white (AC IN N) that I attached to the black and white from the ceiling box. It then had a black (to motor L), blue (to light), and white (to motor n). I then connected those cables to the corresponding cables on the fan black, blue, white (and a ground of course). As I look at the wiring now, I had nothing connected to the red wire... I see this as a problem.

I have taken everything off and would love some help re-wiring this. Which connection(s) did I miss in the ceiling and the wall?

You cannot have the wall switch AND a remote.

You didn't answer my previous question. How was the old switch wired?

I honestly don't remember how the old switch was wired... I literally just took it out and organized the mess of wires that was in there. Sorry... can you help with what I have now? The old switch dimmed both the light and the fan... there was no independent control.

If you didn't know what you were doing why did you "organize the mess"? The mess was correct in the first place.

Unless you have a tester that will do voltage and continuity, and know how to use it, I am afraid it is going to be hard to help you.
You need to identify the (120v) hot line coming into the switch box and then the cable going up to the fan. Once you get that straightened out it is not that hard.
The black and red will be your switch legs going up to the fan, the white is the neutral. At the fan; white to white, black to black, red to blue.

Worse than that-- he has two sets of 14-3 going into the switch box. Assuming one is line and the other is dual switching to the fan, what's the remaining lead for?

Without knowing how it was wired originally, we all are lost.