Finding Common Wire in Old System

Discussion in 'Irrigation' started by firefightergw, Jul 4, 2006.

  1. firefightergw

    firefightergw LawnSite Gold Member
    from Texas
    Posts: 3,340

    I've got a residential that has an old Lawn Genie controller. The real estate company I work with called and wants to get the sprinkler system running so they can lease the house. The controller is fried so much it is even missing the plug cord. I buy a RainBird controller to replace it but notice that all the wires coming out of the wall are plugged into a zone 1-7. Typically white is used for common but it has been plugged into zone 3. I tried to locate a valve box to see what color was hooked up to each selenoid but all the valve boxes are covered. Any suggestions on how to determine which one is common without locating the valves and can the valves be located with a locater without a usable controller wired right or knowing which wire is common?

    Any help would be appreciated.
     
  2. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,794

    Using a Multimeter said to Ohm, try different combinations of wire until you hit one that gives you a reading.

    When you do, you've got a 50/50 chance of getting it right.
     
  3. Rainman7

    Rainman7 LawnSite Senior Member
    from NY
    Posts: 288

    Are you sure that clock was 7 Zones? I only remember seeing 5-6 zone clocks of the lawn genie type. If you wrote down the wire order when disconecting, try the first and last wire together. One of those should be the common.
     
  4. Grassmechanic

    Grassmechanic LawnSite Silver Member
    Posts: 2,697

    ohm meter, as Dirty Water said or with only a few wires, "process of elimination" would also work.
     
  5. If you don't have a meter and cant find a valve. Then start with the process of elimination with different wire combinations for the common.
     
  6. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    Gonna be tough if you have no idea if the valves are manifolded into one box or are spread out.

    Besides the OHM meter giving you an indication the good old trial and error method comes to mind. Turn a station on and then designate one wire as the common and touch all the other wires to the station and see if something pops up. Repeat through all the different wires, switching which one is the common. However, if the system is really jacked up you may not get anything to fire at all.

    The wire locator doesn't care if the wire is connected to a controller or not. It will locate the path of the wire. You might want to disconnect all wires from the controller so you don't get feedback through another wire creating a completed circuit. Unless you know how to read things this could throw you off.
     
  7. This is a really great tip....In my area most of the utilities are also underground. So I disconnect the ground from the utilities also.
     

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