Applies To

Intermatic ST01 Series and EI600 Series in-wall digital timers.

Question / Problem

My ST01 or EI600 timer is switching, but it is not turning on or off at the times I expect. How do I get it back on schedule?

Common Causes / Conditions

• The current time, day of week, or AM/PM setting is incorrect.
• The battery is weak or depleted, which can affect relay operation.
• The timer is set to the wrong operating mode.
• Programming contains incorrect or unwanted events.

Step-by-Step Resolution

1. Confirm the Current Date and Time

   Open the SETUP menu and review the time and day of week. Update them if needed and confirm AM or PM is correct.

2. Test Manual ON/OFF Operation

   Press the ON/OFF button. Listen for a click from the internal relay and verify the load responds. If the display shows LOBATT or no relay click is heard, the battery may be weak.

3. Verify the Operating Mode

   Check whether the timer is in AUTO, RAND, or MAN mode. AUTO runs schedules exactly as programmed. RAND varies scheduled ON and OFF times by approximately 15 minutes. MAN disables automatic schedules.

4. Review All Programmed Events

   Enter the PGM menu and scroll through every ON and OFF event. Confirm each event is assigned to the intended days (for example, MO through SU). The bulb icon shows the event type: an open bulb with lines is an ON event, a filled bulb is an OFF event. Press the + button to step through every stored event and look for unintended or duplicate entries.

Tips / Additional Notes

• Verify AM or PM on the clock and on every programmed event.
• After replacing the battery, recheck the current time, operating mode, and programming.
• Use the "+" button as a final check to confirm there are no unwanted stored events.