Re: lawn sprinkler control unit repair

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

<pak.ecker@xxxxxxxxxxx> wrote in message

> 3) but what confuses me is that I also got a light between each
> colored wire and common when they weren't connect at the valve box

That sounds as if you have a serious, multi-wire dead short to the common
wire at some point.  While I think you've proved the buried cable is bad, if
you wanted to be 1000% sure you'd need to repeat your test but also look for
unintentional continuity on all wires.

I'd do it with a long piece of speaker wire to perform what's commonly
called a loop back test.  At the valve, clip your tester's leads to wire 1
of the head and to your length of speaker or bell test wire.  Run the test
wire back to the console and jumper it to the disconnected end of wire 1.
You've created a loop consisting of  only your meter, the questionable wire
and the (hopefully) known good speaker wire (test it for continuity before
using, just to be sure).

Now comes the important part of the test, and what you I believe you did,
but missed the implications of the first time around.  You must take the
meter lead off the wire 1 and then test each other wire at the sprinkler
head end in turn.  This is the test that will tell you if the wires are
shorted somewhere underground and which ones are shorted.  Any other wire
that shows voltage would be getting it through a short circuit.

So, you should have very low ohms (the light lights up) if the wire is good
when testing ONLY wire 1, and infinity (no light) when testing each other
wire in turn.  After doing the "sweep" of the other cables, go back to
console, connect the speaker wire to wire 2, go back to the head, insure
that wire 2 has continuity and then connect each of the other wires in turn
to determine if there are shorts between the individual wires.  In this test
the light should light up only for one wire at a time.  If you do the
continuity test for wire 3 and wire 5 or wire 2 also lights up, it's
shorted.

--
Bobby G.