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Thursday, July 21st 2011, 5:52pm

0 Volts across solenoid

I have a solenoid question - I get 26+ Volts at the controller (Toro) to my valve, but only 16 volts at the valve. Probably a nick somewhere. I assume that is causing my valve to not work (it works fine when manually turned on). I get 0 ohms resistance across the valve/solenoid leads, which indicates continuity within the valve. Should I get any resistance across the solenoid wires?

But my real question is - I get 16 volts between the common wire (white) and valve wire (red) from the controller. If I connect one solenoid wire to the common white, I still get 16 volts. As soon as I connect the second solenoid wire to the red wire, it drops to 0.0! Could that mean I have a short in the solenoid as well? Or would I get infinite resistance between the common white and solenoid wire? I just assumed connecting solenoid wire 1 to white common wire and solenoid wire 2 to red valve wire shouild still give 16 volts (which is still too low to work the solenoid). I can't figure out why connecting both solenoid wires to the common and valve wires drops the voltage to zero. Any ideas? Thanks for your help and explanations!


Senior Member

Posts: 17

Location: Indiana


Thursday, July 21st 2011, 9:02pm

O ohms is a short and a problem. As far as why your voltage drops to zero I don't have a good answer for that unless you are blowing a fuse which you would have noticed. Your controller could have a feature that kills the voltage to the zone when you have a short. Most I used to work on blew fuses

Matt Dildy

Senior Member

Posts: 17

Location: Fort Worth TX


Tuesday, July 26th 2011, 10:28pm

first and foremost that is a huge voltage drop. some drop is expected and even planned for on LARGE properties but typically a non-issue on your standard residental lot (reason these controllers put out 26-28v although these are 24v solenoids). i would guess this particular zone has been out of commision for some time, low voltage at the solenoid can be just as hard on them as high voltage....wears them out FAST, hence a solenoid reading 0ohms. a good solenoid depending on brand should read between 25-55ohms. the voltage reading dropping to 0v under load and 16v wide open suggests a bad nick and or almost completely severed field wire (ghost voltage). unfortunately these are very hard to find, even with wire tracers/locators. locator has a tendancy to trace right over top of problem without much of a signal drop and or spike. not impossible but takes a very attentive tech who knows how to tweak his locator instead of just blasting a signal at full power. i would suggest grabing a can of paint, renting a wire/valve locator and marking your wire path even if you dont pick up on nick or break in wire mark the path. if the system was installed with color coded multistrand try testing voltage on that same wire at several points, working your way back to controller until you find point at which you get at least 24v. if your wire is all single strand red field wire and white common this task gets alittle harder for average homeowner. all and all if this valve is remotely close to the controller or if you have a spare wire that runs close new to controller or use spare.....there are several other things to mention but thats a start.

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