2 zones coming on at once

I have a 16 zone system with 14 active zones (Rachio model 16ZULW-B). Two of the zones (zones 1 & 5) are coming on at the same time. All other zones work as expected. The firmware for the Rachio is at the latest release. If I start zone 1 directly from the Rachio controller zone 5 also starts and likewise, when I start zone 5 directly from the controller zone 1 also turns on. I replaced the solenoids on both zones but the issue continues. The valves for zone 1 and zone 5 are in two different valve boxes in my yard (about 30 yards apart). If I disconnect the zone 5 wire from the controller and start zone 1, the sprinklers on zone 5 will still come on. Likewise if I disconnect the zone 1 wire (having reconnected zone 5) and then run zone 5, the sprinklers for zone 1 will still come on.
When I operate zone 1 and zone 5 directly from the valve each operates as expected (without the other coming on).
The sprinkler system has been working fine for the past 18 months (when I changed over to the Rachio controller). I have not added or removed anything from the sprinkler system configuration over the past 18 months.
Any thoughts and suggestions on how I might troubleshoot and resolve this issue. Any help is appreciated.

Sounds like the wires are shorted somewhere. Possibly damaged during initial install and shifted to short during Rachio upgrade. Any chance you have a spare wire in your cable bundle? If you get a multimeter, you could verify if your zones are really shorted, but what else could it be?

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Gene - Thanks for your reply.

Unfortunately there are no spare wires in the cable bundle.
I did test resistance on all 14 zones (disconnected power to Rachio prior to testing). All 14 zones came back with readings between 26 and 39 ohms. From what I have read those readings are all within the acceptable range (which I have read is between 20 and 60).
If you have any additional suggestions I’m certainly ready to give them a try.

@BoulderSkies - first off great job on the initial troubleshooting. I’m going to agree with @Gene, in that somewhere the zone 1 and zone 5 wires are joined together.

From the initial testing:

  1. The piping error domain was removed when the zones watered properly when manually activated at the valves.
  2. The Rachio error domain was removed when each zone was removed from its terminal in the Rachio and it still activated with the other zone when the other zone was selected on the Rachio.

I’m not sure the multimeter test would have found anything. It will report the least amount of resistivity in the line, which is one solenoid. We know neither line is open as both lines operate the valves independently in the Rachio.

I’d recommend checking the wiring connections in both valve boxes for those two zones/valves. Posting pictures of the Rachio wiring and the connections in the two valve boxes might give Gene and I other ideas.

And welcome to the community.


Multimeter test I had in mind did not involve measuring impedance on each zone relative to the commons, rather you would want to test impedance between zones 1 and 5. Normally impedance should show 2x average zone value as you would be measuring two solenoids in series, what I expect is a reading that is much lower than any other zone.
Also, in case you are using similar solenoids throughout, reading of 26 ohms suggests that you are measuring two solenoids in parallel as it is roughly half of the maximum impedance of 39 Ohms.
I’m with @DLane’s suggesting to carefully inspect wiring and take as many pictures as you can. Your testing methods pretty much eliminated an issue at the controller and the valves, problem is somewhere between those two things.

Please measure the following combinations with Rachio disconnected
Zone 1 to Zone 3, Zone 1 to Zone 5, Zone 3 to Zone 5.
Let us know the results. Thank you