I have a wall switch and two outside ligthts. there appers to be two black wires to old switch. Timer has white, black, red, and green. I hagve tried all wiring scemes and get lights to stay and not turn off or not turn on at all but can not turn on or off. What is the problem and how should it be wired? Help!!!!!

You posted under the ST01C timer.
ST01C has black, red and blue wires, and has a battery to run the clock.

You have black, white, red and green.
So your timer has an electronic clock and no battery.

Let's go through the wires one at a time.
You can add a comment and I will help further if needed.

Old switch has 2 black wires.
One of these wire is black-Hot
The other wire is black-to-Load (load is your light, fan, motor)

Black-Hot connects to timer-black wire
Black-to-Load connects to timer-red wire
NOW ... if these wires are reversed, the timer will not operate, so simply reverse the wires.

There are two wires to go:
Timer-green wire goes to bare copper wire.
Timer-white wire is the wire that runs the clock inside the timer. This is just like plugging in your alarm clock so the clock runs.

The timer-white wire connects to the other white wires located inside the box.
These white wires are usually twisted together and covered with a wire nut.
So untwist the wire nut and add the timer-white wire to these wires.
What if your box does not have these other white wires?
Then in that case, connect the timer-white wire to the bare copper and the clock will run.

Wiring for GE, Lutron, Leviton, Intermatic, Swilight, Utilitec, Woods, UPM,Tork, Hagar, in-wall timershttp://waterheatertimer.org/Programmable.html#wireWiring for Intermatic ST01C, Ei600, Ei400, EJ351http://waterheatertimer.org/ST01C-program.html#wire Wiring for GE sunsmart:http://waterheatertimer.org/How-to-wire-GE-15312-timer.html

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