"Master valve may have wiring issues and cannot water until fixed"

I’ve had my Rachio 3 installed for about a year now with no issues. In the last month or so I’ve started receiving this error on my phone every time it waters:

“Master valve may have wiring issues and cannot water until fixed”

However the rachio goes on to water successfully, both in reality and in the application notifications.

I’m not sure where to start trying to diagnose this one, any help?

@aaronrach, Here’s what I’d try:

  1. Manually open the master valve using the bleed screw on it and disconnect the master valve wire from the Rachio M terminal and run a cycle.

  2. While the master valve wire is disconnected from the Rachio if one has an ohm meter test the resistivity down the line and back via the Common wire. I think it should be less than 50 ohms.

  3. In addition to the master valve it could be the valve on the first zone that is run as Rachio won’t be able to tell where the power drain is coming from as both the master valve and the first zone valve are opened at the same time. One can swap the first and second zone wires temporarily and run a cycle to see if the error message still occurs when the master valve is connected. Again, I would test the resistivity down the line to the zone valve.

  4. Replacement solenoids are around $9 US, so one could grab a couple along with some water tite/proof wirenuts and replace them if they are older.


Thank you for the advice. That is a much more complicated fix than I was hoping for. So, basic questions incoming:

  1. How do I find where my master valve is? My house was built 3 years ago and everything should be fairly current install tech.
  2. I do not have an ohm meter, though I guess I could rent one for this diagnosis…
  3. If I do find that swapping zones works, what should I replace to fix this?
  4. Where would the solenoid be that would need replacement? Which test above should I use as evidence that said solenoid is bad?

Thank you for taking the time to answer!

@aaronrach - Don’t rent an ohm meter - buy one, they are $14.00 US


The master valve should be close to the backflow preventer for the irrigation system. Start at the water meter and work out. It will be the first valve in the system.

If swapping zones works, I would suspect the first zone. If swapping zones doesn’t work, I would suspect the master valve.