I just installed a dimmer switch and because of it, now my closet, hallway and bathroom lights won't work. The dimmer switch does work. If I revert it back to my old switch everything lights up again. Anybodyhave any suggestions?

Need to do some trouble shooting with a voltmeter to determine the purpose of each wire at the dimmer.. Sounds like the neutral is being switched.

The configuration to the old switch has 2 wires. One is black and one is a red loop with no end. The red one seems like it just had a bit stripped from the bottom. I can't find the ground neither. Is this a common configuration? Btw, this is in a small apartment building.

Are there more wires inside the box? How is the "red loop" arranged" Is this cable or conduit?

It's a cable but it looks like this. The black cable has an end and that's screwed on to the top contact. The red cable loops around the bottom contact with the part touching the metal contact stripped. If you look into the wall, one end of the cable goes up and the other goes down. I thought one was a grounding wire and cut it and attached it to the ground. It worked, only the other lights don't.

Can you take a picture of this box? It would really hep understand what you have.

Ground is green or bare. The red with the loop is probably switch leg to light. Black is hot.
Turn off power, Physically verify connection integrity.
Could have problem with whites.

http://farm2.static.flickr.com/1211/745623674_c97ea27aff.jpg

The Red Wire is where I cut to attempt to pair the one that goes down with the ground. Sorry about the color error, its blue I didn't have the switch in front me of when I said it was black.

OK great, I am starting to see. However, I asked a couple of question I still don't know the answers.

Any other wires inside the box?

Did you use a volt meter to test which wire is hot, which wire is switched, are these wires hot or neutral?

Can you take a pic of the inside of the box? I am guessing you have conduit, a pic inside the box will tell a 1000 words.

At face value, simply changing this switch out to a dimmer and wire it the same way should not cause the problem your having with the other lights. Really need to get the detail I am asking.

Thanks for being patient.

Oh BTW, not nitpicking, but that is why we are here, to teach ,I realize the switch is connected temporarily, but the blue wire is terminated incorrectly, the wire should wrap around the screw clockwise, so the hook closes as the screw is tightened, you show a perfect example of a poor connection. The red connection, not so hot either.

From picture, the red is probably hot, when you said "loop", that sounded like switchedleg,
Sometimes identified with a loop.
From picture, Looks like the red is hot, and needs to be twisted together, and connect to dimmer,
The blue looks like switchleg now, goes to other dimmer wire. Whatever you put to ground undo, What color wire did you put to ground?
Don't have to remove light , but probably has blue and white wire.
That red feeds power to that switch and continues to hall and bath.

Then is there a ground wire?

All you needed to do was, twist the 2 reds(hot in and continuing on to bath and hall). Goes to dimmer also.
Blue also goes to dimmers other wire, blue probably goes to light.
The only ground may be on dimmer, it is green, and connects to green or bare, or could be metal conduit acting as a ground, the box, if metal, will also be at ground potential. What color wire are you putting to ground?

Thanks, but still confussed, when I take new lights off the old ones work correctly.

Something is likely loose in that box.

Blebouef,

You have tack your confusion onto a 5 year old post by someone else. Perhaps you should start your own thread and describe you own problem. Probably get better assistance.