zone valve stays on

I have a six zone valve system (rainbird jarheads). Zone 1 does not shut off when zone 2 is on. From reading previous posts I suspect there is a problem with the #1 diaphram. 5 of the 6 are accessible in the green box and alll of those solenoids will click but I can't isolate which one is for zone 1. ( One of the wires from the controller goes underground beyond the green box,I guess to the 6th zone, instead of to the solenoids in the box. I plan to manually turn on zone 1 at the controller and with a volt meter find the #l solenoid. I can then check for a clog or replace the diaphram. Am I on the right track or is there any advice. Thanks.

 

If only one zone is sticking open when the next zone turns on, and if it otherwise opens and closes okay, when using a manual operation at the controller, then you can employ a simple solution ~ make the troubled zone the last one to operate.

 

Thanks I'll give it a try