American Flyer 596 Water Tower

Unfortunately I can't answer your question.  But I can suggest that if you post it to the S scale forum, the odds are pretty good that someone there can help you.

One wire is for the light, one is for the operation of the spout and one is common. The original colors for the wires were yellow, green and black, respectively. You may need to do some trial and error if it has been rewired.

Hook the common wire (black) to your common post (usually U)
Hook the light wire (yellow) and another convenient length of wire to your voltage post (A,B,C,D). The other convenient length is attached to one terminal of the button.
The operation wire (green) goes to the other terminal of the button. 

The light should be constantly illuminated, and the button should control the spout. 12-14 V is usually adequate. I answered a similar question here.

Thank you that was very helpful!

George

George - you should be able to remove the roof/top of the water tower, which should reveal the wiring 'diagram' -- i.e., which wire is common/ground, which one goes to the light and which to the solenoid that lowers the spout.  The spout on my water tower is very noisy when the button is pushed to lower it.  My guess is that its the solenoid 'rattle' due to supplying the solenoid with AC instead of DC.  If that is the case with your water tower, you should be able to put a small bridge rectifier in the circuit to the solenoid to provide DC.  I haven't done that for my water tower yet, so I'm not absolutely certain that will correct the noise (but I'm fairly certain).  It used to be you could get small bridge rectifiers at Radio Shack, so unless you have a local electronics shop, you may have to use one of the on-line outfits like Digikey or Mouser.

Another change I'd like to make on mine is to install a blinking LED light on the top - in place of the incandescent bulb.  The LED would mean another small bridge rectifier or a hookup to a DC power supply.

- Rich