Sprinkler timers send an electric signal to a series of valves. These valves control the flow of water through an irrigation system. If your sprinkler timer has power but is not communicating with the valves, there is likely a faulty connection somewhere along the line.
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Timer Power Supply
All electronic sprinkler timers use AC power. This requires the use of a small transformer that converts the 110-volt electricity in your home to the 12 volts that most timers use. If you do not have a transformer, chances are the power is too much for your timer to handle and it may have a blown fuse. Replace the fuse located inside the timer box.
Sprinklers use a special type of wiring that is double wrapped to keep it waterproof. This wiring setup usually comes in bundles of seven or 13 wires, enough for a six- or 12-zone system. The white wire is the negative, or ground. Each colored wire represents a single sprinkler zone.
All sprinkler wires end up being connected to solenoids on the top of sprinkler valves. The wiring for solenoids must be kept completely waterproof. Even a single drop of water on the line can short out the solenoid, or the sprinkler timer. Always place sprinkler wire connection points into grease caps, which seal out all water.