Question
Hi Jim,
I have an irritrol total control controller and 12 zones on a large commercial property. I have two issues in two different valve boxes.
The first issue is a valve box that has three valves in it one of the valves works just fine goes on and off with the clock. The other two valves are going on sometimes and other times they do not go on.  
I have 26 volts when the zone is turned on at the controller then when i connect the solenoid to that zone it goes down to 23 volts which does turn the valve on but when i go to different zones and then back to these to zones they do not work. It seems that if I leave it alone for a little while it works again. I changed both all three solenoids in both valve boxes and still have the same issue please help thanks problems

Answer
hey Scott, have you checked the diaphrams in these valves? It could be that the diaphrams are wearing out, and not a problem with the solenoids or the controller. Try replacing the diaphram in one of these valves and see what happens. Good luck and have a great day.