The door goes up, but won't go back down. The green light flashes 5 times. I replaced the RPM sensor and wheel, but I still get the same 5 flashes. The unit is a model 139.53637SRT
Is the trolley jammed against the stop bolt just in front of the motor? If so loosen the chain enough to remove the tension on the trolley. Now run the motor until the door closes. While the door is closed, locate the 'up limit' control on the side of the motor unit. Turn this control 2 full turns in the opposite direction of the arrow printed on the cover. Tighten the chain.