Question
My sprinkler won't cycle through the different zones automatically or manually. I have to remove the top of the hydrotek 6000 valve and physically change the cam position but it won't cycle to the next position after the pump is cycled from off to on. There isn't any debris inside and the spring in the stem compresses normally.

Answer
There are several things to check, according to the manual.

1. Problem: Valve Does Not Change or Cycle to Next Zone or Outlet
Cause: Debris or foreign objects preventing proper movement of stem and disk
assembly.
Solution: Remove valve top and check for foreign objects. Clean build-up from
walls of valve as necessary.
Solution: Check for freedom of movement of stem and disk assembly up and down
over the center pin in bottom of valve. Scale deposits may build up on the pin and
hold stem and disk assembly down. Clean pin and again check for freedom of
movement.
Cause: Disk may have expanded and is rubbing against inside walls of body.
Solution: Replace disk and clean build-up from walls of valve as necessary.
Cause: Restriction of flow causing pressure in valve to build up, preventing valve
from cycling.
Solution: Be sure that all operating outlets are not capped and that the flow to
operating zones is not restricted in any manner.
Solution: The backflow of water from uphill lines may be preventing the valve from
cycling properly. This can happen when the valve is placed too far below an
elevated irrigation line. If the valve cannot be placed close to the high point of the
system, a check valve should be installed near the valve in the outlet line that runs
uphill from the valve.