I have a circa 1993 Craftsman GDO, model 139.53636SRT.

Recently replaced the battery in the outdoor wireless keypad and then tried to reprogram keypad with the manual instructions which tell me to:

1. Press selected code on the keypad...then press and hold the "enter" button. Says keypad will light and blink (I only find it will blink after I let up on the enter button) then:
   
   2. Press the smart button (green on my unit) on the opener end panel and indicator light will flash and the door should begin to move.

Nothing happens in my case. I had someone enter the code while I tried the smart button to be sure we were not using up too much time. The keypad worked fine until I replaced this battery. I have also noticed the indicator light on the unit has started blinking erratically recently. Other remotes work fine.

Any ideas? Thanks in advance!!