How do I install a double dimmer switch onto an existing double switch, I have fitted following the wires as fitted before and the lights will not come on

Try this video
https://youtu.be/NOCHVZi3zXA

It should be;
black wire to brass screw.
white wire to the silver screw.
bare wire to the body of the switch or ground.

Hello, I need a little more info,-
is it for new installation or to replace existing one?
In generall combo switch/outlet comes with its propper colored screws which indicates the position of the wiring, white screw is for neutral (white), single bronce screw is for light (wire that returns from fixture)
double bronce screw which is united by small metal for hot wire(black), I hope it works!

Motion sensing switches wire identically to in-wall timers:
Copy following link for different wiring options depending on the switch that is being replaced:
http://waterheatertimer.org/How-to-wire-GE-15312-timer.html
Copy following link to see illustrations of switch wiring, including motion detector, combination switch, and 3-way switches, double switches etc
http://waterheatertimer.org/How-to-wire-switches.html

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

What are you doing? I can't figure it out.
I think you have a new double rocker switch and you are trying to replace a double toggle switch and you don't know which side to put your wires?
The screws are color coded. Look at the screw colors on old and new switches and follow same pattern.

If this is incorrect, answer back and I will help.

If you are adding another circuit.
That means running a new wire into the box to power another receptacle box, or to switch another light fixture.
If this is the case, the best place to connect any new circuit is the existing receptacle.
Connect new black wire to brass colored screw
Connect new white wire to silver colored screw.

You're correct. The dimmer switch was not made for that fan.

The Green is ground > so you're right there too. I assume other plugs nearby are working when dimmer is on. Check that to make sure.

By your description, I assume there is NOT another switch or dimmer that connects to same light. If so, you need a 3-way switch and the following instructions are void.

I suspect when you wired the new fan, that you saw the red and small black wires in the ceiling box. Did you connect the fan and light to those wires? If so, the following information will help you wire the switch.

Your incoming Hot line is probably the larger black wire that connects to Dimmer black >>> this wire will connect to either screw on the new switch

To test Hot wire for sure: Take out dimmer and mark wires for identification. Separate wires. Turn on power and test each wire to bare ground. Tape tester leads to wood sticks so hands are away from power. You'll be fine. Tester lights up on Hot wire.

Next: The smaller black and a red wires are a toss up.

Here's how I would proceed. Connect the black Hot to either screw on switch. Connect red wire to other screw. Put wire nut over small black. Turn on power. Flip switch. Check both lights and fan to see which works with red wire.

Next reverse the toss up wires. Put wire nut over red. Connect small black to switch. Check both lights and fan.

If red and small black control the light & fan, then connect them together on the same screw, and you're done.

If you want to control the fan and light separately, buy double switch, and then Hot connects to dark-colored screw on one side of switch, and red and small black connect to two different screws on opposite side of switch.

The white and the black wires are both hot wires, and the green wire is for earth ground only. The green wire does not belong hooked up to the white wire.

The two black field wires should be attached to one side of the dimmer switch (one of the black wires from the dimmer switch)

The white field wire should be attached to the other side of the dimmer switch (the other black wire from the dimmer switch)

The green wire from the dimmer switch should be hooked up to earth ground only (any un-insulated copper wire that is inside the switch/outlet housing) and if you can not find it attach the green wire to the inside of the light switch outlet housing and be sure that it is attached to metal.

The other hall light switch that you are talking about must be connected inline with that light switch you trying to turn into a dimmer, and it should operate again nomally once you have connected that light switch properly, and if not check for any tripped circuit breakers.

I have fitted several dimmers that just use the 2 wires, follow the instructions, you might have to work out the hot lead though.

quite possible measure the input and the secondary output - you'll get your answer.

When you take the existing switch out of the wall, the existing switch will have one black screw and two gold screws. The wire that is connected to the black screw of the existing switch (probably on of the black wires from the box) connects to the black wire on the new dimmer. The other two wires (one black and one red from the box) that are connected to the two gold screws on the existing switch will connect to the two red wires on the new dimmer. Basically, wire from black screw goes to new black wire and wires from gold screws go to new red wires.