On Thu, 24 Aug 2006 23:19:07 GMT, "Dallas"
wrote:



I've got a real head scratcher.



Long story short: 18 zone, 24-volt AC commercial sprinkler controller
system.



One valve on the system won't operate anymore after running fine for years.



The valve operates when connected to a battery operated testing unit.



Voltage at the controller terminal going out to the zone shows 29 volts.



The wires from the controller at the valve (guessing 200+ foot underground
run, 14 gauge wire) show 27.4 volts.



There's enough current to give you a tickle if you grab the wires.



Connect the 27.4 volts to the valve and nothing happens.





My degree was in Business so I start to get fuzzy at this point. Could one
of the wires be missing some insulation somewhere underground and drawing
off enough amperage to keep the solenoid from actuating while still showing
27.4 volts?



Is there anything that could happen to a solenoid coil that could make it
demand more current to operate?



Sadly my $30 meter doesn't have an amperage function. Would hooking the
voltmeter in series with the circuit tell me anything?



Can anyone give me a clue as to what's going on?



Dallas

You want to measure the voltage with the solenoid valve connected to
the power source. They use solid state drivers (triacs) that will
leak enough voltage to appear to be working when they still won't
operate the load if there is no load connected)

If it still doesn't work, switch that channel to another zone and see
if it will work that zone.

One assumes you tested the water supply?

I'd also see what an operating valve uses (what voltage is across it).
Choose a valve the same distance from the controller and measure that
voltage while it is on. 27.5 sounds too high considering nominal is
24 and you should drop some voltage in the line - I know you think it
is connected but that sounds like it isn't. (wire nuts?, corrosion?)

Failing all else, bite the bullet and replace it (or physically switch
it with one of the other's - if that's an option - to see if the
problem stays with the valve).

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