Hiccup while changing wall switch to dimmer

Trying to change switch in my MBR to a dimmer. Seeing something unusual.

Looks like thick wire (what's regular gage--16?... Then this is 14) two conductor on one side, 3 conductor "normal thickness" on the other

Black on both side connected to one side of switch

Whites connected directly together

Red connected to other side of switch

What is this? Are they "splicing" two blacks at switch? Was this a 3 way at some point? There is no sister switch that I am aware of

This switch does control ceiling fan light. And it's on same circuit of rest of bedroom (wall outlets)

Can I just connect new dimmer same way? (Switch has one black wire using push in connection, the other using screw, red wire using other push in connection on other side of switch

I'm on mobile device. Have to figure out how to add a picture

Here is link to pic
http://i771.photobucket.com/albums/x...CFC1C335BA.jpg

 

You probably have the power to the fan (black) and the power to the light (red). Do you pull a chain to control the fan?

One is switched by your switch, the other is not.

If the fan stops when you turn off the light, then the red wire powers both, and you cannot add a dimmer for the light without adding new wiring.

 

The second cable likely goes off to feed outlets or another switch somewhere, it's not an unusual arrangement. Or it may be the feed, bringing power to the switch and light.

You will want to wire nut the two black wires together along with a another short piece of black wire. The other end of the short wire goes to the black or hot terminal of the dimmer. Red goes to other terminal of dimmer. Your dimmer may need a neutral connection (white), in which case you would add a short white wire to the other whites. You will also likely need to add a short piece of bare wire to the grounds that are present, to run to the dimmer as well. Unfortunately, that looks like a pretty small box, so it may be a challenge to get everything to fit. Just carefully fold and push the wires as far back as you can.

Don't use the push in terminals; they are often unreliable. Use the screw terminals. Hard to tell from your pictures gauge of wire, but it will be 14 or 12. 12 is bigger than 14, but you can't go by the thickness of the insulation, you have to look at the wire itself.

Turn the power off!

 

You guys nailed it. They combined the fan (little black wire) and the line using screw and push in connection for "always on"

The red was for the light

I expected this should have been done with twisting the black wires together and a jumper to switch, but it was apparently amateur hour here