Craftsman GDO Closing Problem, Please help..
My Mother-in-law has a Craftsman 1/2HP 139.53900 GDO that opens fine but when closing it goes down a couple inches, reverses then the light flashes. The door can be closed by holding the button down from inside the garage. The sensors are in perfect alignment. Another symptom is that some times the light will come on for the 4 1/2 minutes then go off all by itself. It does this at all times of the day and night. The green light on back of the unit also blinks 5 times intermittently. I read somewhere that this might be caused by a bad RPM sesor. Could this be the problem or is it possibly a bad sensor, control circuit board or something completely different. The unit is 6 years old and I hate to replace to opener unit unless absolutely necessary. Thanks in advance for your help.