Howdy,

I need some expert advice.

After 13 years of no problems, I have one zone that will not shut off. The system was in the house prior to when we purchased so not sure exactly how old the system is. We are on city (Denver) water. The controller is a Rain Bird ESP 8 SI. I have 7 zones. The valves are a mix of a brand called Lawn Genie and what look to be Rain Bird. There is a master control valve as well.

Zone 1 comes on and does not shut off. The controller will cycle thru and turn on the other valves but will not fully operate the other zones with the zone 1 valve already open and drawing all the pressure. Although pressure does drop for zone 1 and some water come out at the other zones. The master control valve is working properly as it starts and stops water flow to the system.

Here's what I've done so far with the help of the Rain Bird Troubleshooting Guide.
http://www.rainbird.com/documents/diy/IrrigationTroubleshootingGuide.pdf

Checked for constant voltage to the solenoid. Nope.

Checked resistance for the circuits for all valves in the box and from the connections at the controller. No shorts or open circuits. Resistance at 25 - 35 ohms on all circuits.

Replaced the diaphragm and solenoid on #1 valve. Checked for debris in the various orifices. No different result.

Replace entire valve with a similar Orbit model from Lowes.

http://www.lowes.com/pd_249620-74985-57661_4294713292__?productId=3133363&Ns=p_product_qty_sales_dollar:1&pl=1ätURL=%3FNs%3Dp_product_qty_sales_dollar%7C1&facetInfo=

Disconnected all the electrical connections (to all valves in the box) and turned on the water to the system at the master control valve by turning the solenoid a 1/4 turn. Zone 1 come on. I initially was just checking for leaks when replacing the valve and was surprised the zone came on.

I'm now scratching my head. I can only speculate its too high water pressure keeping the valve open. But why now after 13 years? And why only that zone?

Please, help. Lawn dying (except for zone one). Drought conditions.

Thanks
Mark