Hi, I have a sconce light on the front of our house that I wanted to put a photocell on so that we can leave the switch on and it will operate itself during the day/night.

I have 2 sconces on our back deck with built in photocells and cfl bulbs that work perfectly. The front sconce is a different manufacturer - standarb bulb size but didn't offer a dusk/dawn model. So I bought an intermatic one and it works perfectly at night but during the day it cycles on and then quickly back off... it continually does this. I replaced the cell with another intermatic one, same thing. Today I bought a different brand and a slightly different type with a bigger window on a swivel. After just hooking it up, same results. Thought maybe it's a CFL problem so I put an incandescent in it... doing the same thing.

I have the wiring correct (pretty sure) with the red line to the load (black power in) and the black line to the lights' black power line. All the whites are tied together.

I'm stumped and it seems like this should work.

PLEASE HELP!

That's odd, you have it wired correctly. A problem with photocells at night can be when it gets dark, light comes on, photocell see light, thinks its daytime, goes off, then photocell sees dark and will continually repeat.
Is is a little dark/shaded on that light?
Try shining a flashlight on photocell and see if it stays off.

Yeah, and I have the opposite issue. It's the daytime function. I did shine a super bright LED into it and it does the same thing so I don't think it's a light level issue. I'm going to switch the black and red for shi_s and giggles and see what happens. So I'll have the black power into the light to the black wire on the photocell, the whites tied, and the red wire on the photocell heading out to the black wire on the sconce.

The Black is the line side(constant power).
The red goes to lights black.

What threw me was "red line to load", red line does go to load, the load is the light, the line(constant power)is the line and goes to black.
I think you've got it now.

That appears, cross my fingers, to have solved the problem. Wow, I'm an idiot!

Stuff happens.