An auto timer switch is a simple electromechanical device that automatically toggles on and off on preset intervals. They are commonly used in gardens to control grow lights, sprinklers and pumps. Though they come with a manual it can be rather unintuitive to operate them specially for beginners.
Auto Timer Switch Overview
An auto timer switch has a large dial in front what rotates clockwise and doesn’t rotate the other way. The whole dial corresponds to a 24-hour day. The solid black arrow indicates the current time and larger arrow indicates the direction the dial is turning. The numbers indicate the time of day and between them are tick marks indicating 15-minute intervals. Also notice the line joining the tick marks from “18” (1800 or 6:00PM) to “6” (0600 or 6:00AM) this means these hours are night-time hours and the rest are day-time hours.
Around the dial are ninety-six individual buttons that can be depressed. There are four buttons under each hour indicating fifteen minute intervals. When depressed the button is in the “on” position. This is how the timer switch is programmed. The buttons are depressed for the times that the switch is supposed to be “on”.
To one side of the timer switch is the mode switch. When the clock figure is visible then the switch operates in “timer mode”. “On” for the times a black button is depressed and “off” otherwise. When the “I” figure is visible then the timer switch operates in “always on mode.” It is always “on” regardless of how the dial and buttons are positioned.
Timer will always be in the “on” position when the “I” figure is visible. 
Timer will operate normally when the clock figure is visible.
Just below the dial is an outlet where you plug in the appliance that you want to be controlled with the timer switch. To the side is a pilot light. When the switch is “on” the pilot light is lit and unlit otherwise.
At the back of the timer switch is a two prong plug which goes to a wall outlet when the switch is operating and a label indicating the device’s specs and limits.
Auto Timer’s Two-Prong Plug 
Operating Limits
Auto timer switch operation.
- Depress the small buttons for the times of the day you want your device to be powered on. Each button represents fifteen minutes of “on time”.
- Rotate the dial clockwise to align the numbers on the dial to the current time. Consult your clock for the current time.
- Make sure the override switch shows the clock figure to make sure that the switch is operating in timer mode instead of always on mode.
- Plug in the timer switch to wall outlet.
- Plug in your device or appliance to the timer switch
- Turn your device or appliance. If the pilot light on the timer is on your device or appliance should be on as well.
The video below demonstrates these steps and shows via a time-lapse how the timer switch operates.
Things to remember.
Always consult your timer switch’s manual. This guide is only a general overview of how the auto timer switch operates. There can be differences between brands and models.
Most timer switches are designed for indoor use and is not water proof. When gardening indoors it’s a good idea to always have all electrical equipment at waist level. You can use a splitter if you one more than one appliance to be controlled by your timer switch. Always take into account how much load your timer switch can handle.
During power outages your timer will stop operating. When the power comes back on you must manually adjust the dial to correct the time. If you want intervals finer than 15 minutes or if you want the timer to remember the current time even during power outages, you can use a digital timer switch that runs its own digital clock and has finer intervals of on/off time.
I hope this helps. Feel free to leave a comment if you have any questions. Good luck and happy growing!