Why does a garage door opener with or without the door hooked open only a foot or two and then stop and does the same if the door is open and you try to close it?
I am not a garage door opener technician, only a user for many
years. The following answer is based on my experience, and
hopefully will be replaced or improved by a professional.
Many garage door opener manufacturers, in order to make their
product SAFER, have added a circuit in the motor, which measures
the amount and changes in the operating electrical current. The
purpose of this is to detect anything blocking the movement of the
door [e.g., a child, a person, a pet, a vehicle, etc.] Even
"dragging" bearings/bushing INSIDE the motor can cause this.
Upon detection, the door is supposed to stop, and, sometimes,
even return to its previous stopped position [usually full open].
ANYTHING, which causes the door motor to "work harder," can trick
that detector and cause the situation you describe.
If there is nothing blocking the door, I have found that
"dragging" rollers, or bearings/bushings inside the motor,can cause
the problem. If this is the cause in your case, then you probably
can correct it.
First, carefully CLEAN all accumulated dust, dirt, lint,
cobwebs, grease, etc from the tracks, the rollers, and the roller
axles. Then carefully lubricate all roller bearings/axles with JUST
2 or 3 DROPS each of any clean oil. Do NOT overlubricate as this
just encourages more accumulation of debris.
Another possibility is that some, or all, of the rollers and/or
their bearings/bushings are worn out, causing the drag, and then it
will be necessary to replace them. These parts are usually
available at your local hardware stores, or home improvement
warehouses like Lowe's, Home Depot, etc.
IF your problem is caused by "drag," then proper cleaning and
lubrication will fix the problem. Also, drag can be caused by
misalignment of any of the tracks, and or bending damage to the
door or tracks. Good luck 1 j3h