Weathermatic Valves stay open
I have a sprinkler system that was installed in 1997, prior to my owning the home. All components (controller, sprinklers, valves) are Weathermatic. The valves, from what I can tell, are similar to the current 12000 series. They have solenoid # M 21E if that help at all. I have 5 zones and 2 of them stay on either partially or fully when the solenoids are not energized.
Should I try to replace the diaphragms in these 2 valves or just replace the valves (or all 5 of them) all together? Also, is the 12000 series a good, economical choice for my application since these valves have worked for approximately 13 years?
Thanks.