If you reset ST01C timer using reset button, then all programs are lost, plus current time of day.
Generally this timer needs to be reset if error message appears and as last resort for troubleshooting problem. Timer does not need to be reset after battery goes bad, all you do is set current time of day, and then program remain inside timer indefinitely (or until timer is reset of goes bad)
If setting current time of day does not work, you use reset button.
For ez programming steps with illustrations:http://waterheatertimer.org/ST01C-program.html
How to reset ST01C using reset button:
Push and hold ON-OFF button and then push reset button using toothpick or paperclip.
Release reset button but keep holding ON-OFF button until INIT displays.
Then release ON-OFF and 12:00 should be flashing.
If timer functionality does not restore, then try replacing timer battery.
If functionality will not restore, then timer is bad.
This timer does not need electric current for setting timer, so timer display is not dependent on circuit breaker.
If you have a different timer, then add a comment with in-focus photo of timer for possible identification. Most other timers do not require 2-button reset procedure.http://www.fixya.com/support/r6568559-post_photograph_fixya_questions_answers
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