The COMET Keypad is the first place to look for trouble with this timer. Remove the rubber feet from the back and remove the small phillips head screws that hold the two parts of the shell together. Open the timer so that the battery part of the shell is seperate from the controls. Leave the two connected. The keypad control cable is the clear cable with the blue connector. Remove it and reinstall it a couple of times. Very often this cleaning of the contacts will solve the problem. If the keypad is really worn it will need to be replaced. It is held on by adhesive and will peel off. Buy a new one, thread it through and restick.