Sometimes referred to as controllers, timers on sprinkler systems control when a set of sprinklers will begin watering and how long they will operate. The user programs the timer to start the watering cycling at a specific time on certain days, and sets the duration of the watering time for each zone or group of sprinklers that water a defined area. If a timer is not operating properly, the sprinklers may turn on while children are playing on the lawn or during a family get-together. Incorrect programming is the most common problem affecting sprinkler timers.
Extended Watering Cycles
Some timers can be programmed with more than one start time; each one is referred to as a program and are typically labeled A, B, or C. If the start times overlap, the sprinkler system will run for an extended period of time. Once the system is activated by a start time, each zone will water in order. If the second start time occurs before the first watering cycle is completed, the timer will switch back to the first zone and repeat the cycle. If several start times overlap, the system could run continuously. To correct the problem, clear the start times and reset them to allow enough time for the program to cycle through all the zones.
Watering Cycle Does Not Work
A watering cycle will not begin if a start time and the length of irrigation time are not programmed into the sprinkler timer. If the timer is programmed properly, but the timer still does not work, it may be defective. To check the timer, use an omni-meter or voltmeter to check the voltage at the station terminal screws. Each station terminal controls a zone; activate each zone and verify that the reading of the corresponding terminal is between 24 and 28 VAC. If the readings are not within the specified range, replace the timer. Some timer models have individual station modules that are replaceable.
Display Screen Problems
The display screen on a sprinkler timer will be blank if it is not getting any electrical power because it is not plugged in, the outlet is defective or the breaker has been tripped. If the timer has a backup battery, the screen may show “NO AC” or “NO” to indicate there is no electrical power going to it. If the display screen is blank, shows partial letters and numbers, or reverts back to the time while the user is programming the timer, the circuit board may be defective. The circuit board can be damaged by moisture inside the timer, a lightning strike, a power surge or a defect in the wiring between the timer and the valves. A timer with a defective circuit board will have to be replaced.
Other Timer Problem
If more than one valve is opening at a time, the wire from a valve to the timer may be defective. The electrical current can transfer from the station with the defective wire to the adjoining stations, which will activate the corresponding valves. Check the electrical wires and replace any that are broken or damaged. A bad fuse in the timer or a defective timer can result in a valve not operating, although the display screen indicates the zone is watering.