I recently replaced the tension springs and the sprocket on my craftsman 1/2 HP garage door opener. The sprocket had gotten shredded after the springs getting stretched out and not bearing much weight. Now that I've reconnected everything, the garage door motor starts to lower the door (not raise it) and only goes about 8 inches before it reverses. I set the door in the open position to allow it to close. I adjusted the travel limits all the way up and the same with the Force limits but the motor still does the same thing. Any ideas?
Resetting the door to start in an "open" position as the motor tries to close the door every time it is activated. Also increased the Travel and Force limits all the way up.
Hello and welcome to Just Answer.
Sounds like the RPM sensor is most likely defective and needs to be replaced or it may still be good since you say you were replacing the gears. You may have accidentally disrupted the sensor or covered it with grease.The RPM sensor is a little circuit board located at the door end of the motor shaft, inside the motor unit. They are relatively easy to purchase and install. The RPM sensor is what causes the door to reverse when it hits something. When the door hits something the logic board doesn't receive the pulses sent by the sensor and it reverses. When this sensor goes bad the door will start down and the logic board will not receive the electronic pulses and it will reverse, just like yours is doing. Take the cover off the unit and you will see a black cap on the end of the shaft that rotates between infrared sensors. That small circuit board is the RPM sensor.If you need further help or clarification on this answer, please do not hesitate to reply to this post.
Licensed Architect- 16 years, L.E.E.D. AP