Model 139.53985D, 1/2 HP chain drive
Started having a problem opening/closing the door, it would move 6" at a time then shut off (thermal protection I gather, however if I tap the unit the power will come back on.
The diagnostic light flashes 3 times signifying it's a wall control or wire to the wall control problem. Per the manual I determined the wire to the control was the problem (the motor would start up when I shorted a wire across the 2 terminals). I connected a new wire and had same results.
After reading as much as I could find it sounded like the RPM sensor because the door would move 6" and stop. I changed the RPM sensor and the interruptor cup, same results.
I've had the door disconnected to remove that from the equation, and I unhooked the wall control. The safety reversing sensor lights (amber and green) are glowing steady, no flickering, etc.
I don't know if this is a logic board issue or what, the diagnostic light flashing 3 times points to the wall control as the cause. So I'm considering buying a new unit. This unit is about 4 - 6 yrs old.
Thanks for any help!