Find short circuit

[stuartmit]

I am using dual coil solenoid switch machines of the sort the NJ International and Tenshodo and others make or have made. I wire directly to the three terminals, ignoring the extra contact sets which you can use to control signals. I supply power from the C terminal of a ZW and control the machines with push buttons from Radio shack which allow grounding the coils back to the U terminals of the ZW. Somehow I have picked up a short such that I am witnessing the following behavior; Tbe C circuit of the ZW is blowing the breaker. IN an effort to locate the short, I disconnected that wire from the C terminal. Now I have one machine which is getting energized in some way because I hear it buzzing and manual operation of the switch is resisted --so One coil is energized in some way through some path, and I suspect if I understood how this was happening, I could find the short. I suspect that in some way both coils are in an unintended circuit which includes the leads to the coils which originate at the push buttons. The push buttons are normally open, so some how both leads must be setting up a circuit by incidental contact with some other unintentional source of power. No question my wiring technique not the best, but the system has been in place 2-3 years and no problems until last week then I was powering up a new yard, in which the turnout with the afflicted machine is NOT involved, and which is 18-24" away, so I doubt there is unintended contact of wires. But I guess what I probably need to do is undo my work from last week to get back to my last known "stable" state, and then go forward carefully. any suggestions are appreciated.

[Dave632]

 I agree with going back to before you made any changes and work from there. Also do not leave the switch that is constantly energized powered or you will eventually burn out the switch.

[stuartmit]

A little more info: With the C ring turned off, for some reason, I touched a wire to the D terminal of the ZW and the other end to the "downstream terminal of the radioshack push button. The switch snapped right over, so I know the coil is not burned out. That worked for both coils. Not sure why I did that, but it at least told me the coils were not burned out. I have all sorts of thoughts which I can't figure out> For example, if the push button had failed, and thus was constantly closed, and if the wire coming from the C ring had become detached, then the electricity would attempt to complete a path through both coils, which would lead back to the other push button which might have also failed, but even that would lead back to a feeder of the same potential, so there would be no current set up; they would both be at the same potential energy level. ANd I Believe the push buttons are in good order. I think my only solution here may be to completely dismantle the installation of the machine and feeders and redo it, hoping to eliminate the unknown and unintended circuit. Not a prospect that calls to me, and I think there is a reasonable chance that it might not work.

[servoguy]

If you don't have a meter, you would be well advised to get one.  Harbor Freight has them for about $8