How to Replace a Sprinkler System's Control Wires

Unplug the sprinkler timer or turn off the main electric breaker to the house. For added safety, do both.

Remove the cover on the sprinkler timer.

Write down the order of the wiring in the panel. The white wire is usually labeled as the negative wire, while each colored wire represents a single zone. The screws that hold the wires in place should have a corresponding number. Write down the color of each wire and the number of the zone.

Unscrew each of the screws that are holding wires in place. Gently pull out the old wires.

Remove the grease caps on the ends of each wire within the sprinkler irrigation box outside. Write down the color of each wire and the number of the valve that it leads to. If the red wire leads to the first valve, for example, write down "red 1."

Remove the wiring from between the control timer and the irrigation box and discard.

Lay out the new sprinkler wiring from the control timer to the irrigation box.

Strip off at least 1/2 inch of insulation from the ends of each wire on both sides of the new wiring.

Insert each end of the new wiring into the slots on the control timer based on the color order that you previously wrote down. If the old red wire went into the first slot, place the new red wire into the first slot. Secure each wire by turning the screw above it until tight.

Set the wiring at the irrigation box into each of the grease plugs in the same order that you previously removed them. If the red wire was attached to the plug leading to the first valve, insert the new red wire into the same plug. Replace the caps on each grease plug.

Plug in the sprinkler timer and turn on the main breaker.

Set the sprinkler timer to the "run" position and check the functionality of each zone.