Saturday, August 4, 2007

Lawn Sprinkler Controller Replacement

Changing out an old controller to a new one is quite simple. The steps are outlined for you in this do-it-yourself article. When you have done it once, you will realize how easy it is.

Lawn sprinkler timers are the “brain” of your irrigation system. It tells your valves or zones when to turn on and for how long they are to run.

Until approximately 15 years ago, mechanical controllers were the norm. Since then digital controllers have all but made the mechanical controllers obsolete.

How do you know which type of controller you have? If you have a digital controller, it will have a display screen indicating what day it is and what time it is. All mechanical clocks have a “wheel” or dial that you turn by hand to set the day and time. The mechanical controllers do not have a digital display.

Keep in mind, any system with moving parts requires maintenance or replacement. Whether it is parts for your automobile, for example, or parts of your sprinkler system, nothing lasts forever. The purpose of this article is to lead you through the steps of how to replace your sprinkler controller (timer). Changing out your old controller to a new one is quite simple.

The steps are outlined for you in this article with the goal of empowering you to successfully replace your sprinkler controller and to realize how easy it is to replace your worn out or out-dated one.

Please read the full description of “how-to” steps before beginning the removal of the old sprinkler controller.

Step #1

It is important to write down the existing program on the old controller. Include in your notes what days to water, what time to start watering, and how long for each station (zone). You can change the program later if you would like.

Step #2

After writing down the program, unplug the transformer from the wall (flat square plug similar to a cell phone charger) or turn off the power to the controller at the breaker. VERY IMPORTANT: Do NOT go any further until you are absolutely certain that there is NO electrical power to the controller. If unsure, check the power input wires with a volt meter, or call a licensed electrician. Electrical power can seriously injure or kill you. Once you are certain you have disconnected the power, go to step #3

Step #3

The wires that control the sprinkler valves are inside the controller. Now you must remove the face of the timer to manage the valve wires.

Step #4

Disconnect the field wires from the controller and label each one with a piece of tape. As you remove each one, label each piece of tape.

Here is a guide to how to label the wires:

*The two most important wires to pay attention to are the COMMON and (if your system is run by a pump without a pressure tank) the PUMP START WIRE.

*The common terminal in the controller is usually marked by the letter “C”.

*The pump start terminal will be labeled either “PS” (for pump start) or “MV” (for Master Valve). NOTE: if you have a mechanical controller that you change zones by toggling the ON/OFF switch, you will have only two wires going out of the timer,

you should replace your timer with the same model and brand as you already have on your system. Even if you do not run your system with a pump, you may still have a master valve; therefore, label it.

*Frequently, all the field wires will be a different color. This makes things easier. Simply write down which color wire relates to which terminal, (example: white is common. Red is Zone 1. Green is Zone 2, etc.).

Step #5

Unscrew the old controller from the wall and mount the new one. Take care to mount it in a position that will accommodate the existing wire. If the existing wires are to short to reach the connections for the new controller, you can extend the wires and place the splices in a junction box. NOTE: If you are using a junction box outside your house, use a waterproof junction box.

Step #6

Re-connect the power wires and turn on the breaker or plug in the transformer. Next, connect your zone field wires and test that every zone comes on.

Step #7

If you have a rain sensor (you should get one if you don’t have one on your sprinkler system already), the connection for the common and PS/MV will be different. The rain sensor will have two wires. It acts as a switch between the common and the PS/MV wires and the valve/field wires.

  1. If you do not have PS/MV wire: Connect one of the two rain sensor wires to the common wire. Connect the other rain sensor wire to the common terminal. If your controller came with pre-installed rain sensor terminals, use those instead.
  2. If you do have a PS/MV wire: Instead of connecting the rain sensor between the common wire and the common terminal, connect it between the PS/MV wire and the PS/MV terminal instead. This will prevent either the pump or the master valve from coming on after it rains. This is especially important in regards to pumps operated by a pump start. You do not want a pump running against as “dead head”. This means that a running pump needs to be able to discharge water or damage to the pump can occur.

Step #8

Your system controller should be properly functioning and ready for programming. Referring to your program notes you wrote down from Step #1 (information from the old controller), program your new controller. That’s it. You’re done.

Although sprinkler controller may seem complicated, the cost-saving and careful do-it-yourself replacement of one is easily within the ability of the average homeowner.

This information is meant to be instructional and to provide information to assist the consumer. The information is believed to be accurate. Craig Borglum, Craig Borglum Inc. and Irrigation Repair Inc., assume no responsibility for any damage that arises from any action based on information found in this publication.

About the Author

Craig Borglum is a Nationally Certified Irrigation Designer, Irrigation Contractor, and Certified Irrigation Water Auditor with more than 25 years experience and formal education in the field of irrigation. For more information regarding water conservation, articles and tutorial Lawn Sprinkler System Repair DVD, visit, or write Craig at


Willie said...

I need help with my lawn sprinkler mechanical timer it is a Hydrotek model # 1114 some of the wires came apart when i was trying to kill and get rid off the wasp's nest. Now i don't know which wires go together, which one go to solenoid, trasformer, power etc. can anybody help??

Craig Borglum Irrigation Repair said...

Hi Willie,
A Hydrtek is pretty much the same as a K-Rain indexing valve controller. You have 120 or 240 power in and a 24 volt out (sometimes high power out as well if it has a pump)to a solenoid master valve that controls the indexing valve. If you go to this website and scroll to the bottom for instructions, you can print the manual. As a precaution,always use a volt meter to check the wires or terminals before you touch them. Craig