There is no repair for defective timer.
Sounds like the timer could have a conflicting program.
1) Good idea to test outlet with cheap circuit analyzer to make sure electric outlet is not causing problems for timer electronics.
2) Press reset button on timer face using toothpick to Re-set the timer
This will clear programming and then timer is ready to start over.
You can unplug timer from outlet while programming timer, so buttons and display are easy to see.
3) Open following link for clearly written instructions:http://waterheatertimer.org/How-to-program-Utilitec-0155671.html
4) I suggest setting timer program1 ON at 7:00pm, and choose all-days-of-week
And then set program1 OFF for 11:59pm all-days-of-week
Setting to 11:59 pm instead of 12:00 may solve problem.
5) Open following link for Kitchler manual:http://waterheatertimer.org/pdf/Kitchler-15558WH-timer.pdf
6) If timer will not program correctly, and electric circuit is clean, then timer is defective.
This timer has 1 year limited warranty against workmanship defect.
I always suggest buying timers at local store because returns are cheaper, and if timer goes bad two years later, you can buy new timer and return defect in new package.
Kitchler is same timer as sold by Utilitec at Lowes, and Westek at Target.
7) Take a moment and rate answer:
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on timer or any do-it-yourself project.
Fixya is always less expensive than a service call.