Preparing to have my 5 zone underground sprinkler system winterized next Friday I discovered that two valves on adjacent zones are not opening. (I had this problem on a different zone last year but the problem did not occur when starting up in the spring and the zone worked fine all season. Fortunate for me because I have no idea where the valve box is for that zone.)

I opened the valve box for the current problem zones and was able to get water flow manually by unscrewing the solenoids. There is a third zone valve in that same box that is operating OK, so I tried each of the other zones with that solenoid and they operated fine.

I have three ways to energize a zone: Timer on automatic, timer on manual, exterior service switch that mimics manual operation--none would operate the problem zones.

I have checked for voltage at each solenoid using a Klein NCVT-2 tester and each zone wiring tests fine for 24 VAC when energized.

From this I am concluding that two solenoids have failed and need to be replaced. I have ordered Toro Jar-Top solenoids from HD but the magnet end looks slightly different than the existing. HD allows returns if they don't fit.

Does this sound like a reasonable assessment and resolution for the problem or should I be checking something else too?

The new solenoids won't be here by Friday so we will open the valves manually to blow the zones out.

 

Finding 24vac at the solenoids and them not operating usually means they're bad.
I like to check them for continuity with an ohmmeter before replacing them.