I installed a new 3/4 horsepower Craftsman garage door opener. Went
well, no problems. Close position set and open position sets well.
However, when in the open position, and I push the botton to close the
door, the initial motion is extremely bouncy and tourques the arm
upwards before continuing on it's path to close.
The mounting is solid and the open position is proper (i.e it is open
just short of level and not at a backwards slant).
Is my problem the angle of the arm from the wall to the motor unit?
Or...any other ideas?
The following is assumming your door is running on overhead tracks
(sectional door) and not a 1 piece door with or w/o track. As I presume this
is the 3/4hp chain drive, (53990) you will get some initial torque when the
motor starts up due to chain slack.
Check to see if the guides have any rack in them. This can cause some
binding leading to your start-up torquing of the door mechanism. Rack being
the diagonal measurments of the guide frame.
|\\ / |<<measure digonally from ends to a given point of the
equal length along the guides
| \\ / <------- Diagonal rack
| \\ / |
| \\ / | This would be a view from the top or bottom of the
| \\/ |
| / \\ |
| / \\ |
| / \\ |
|/ \\ | <given point> Can be 10',12', 14' etc. etc. Just a
check to make sure the guide frame is "square" and not a parallelogram
(http://mathworld.wolfram.com/Parallelogram.html ) nor a trapezoid (
I hope 'just short of level' is somewhere around +/- 3/16" in 8' from track
to track. (IE: Both tracks are @ the same elevation) In reality, the tracks
need not be dead level from the door frame opening to the end of the tracks
by the motor, but it's better if they are. You can also check to see if the
door is binding, when in the up position, by using the manual release. Pull
the release and push the door to the down position, see if you are getting
any initial binding in the full open position. If it's binding in the
uppermost position, it should be fairly noticeable because the door will
hang and then travel quite freely after you've moved it down some distance.
You can also test this theory by lowering the upper limit in the full open
position. Say you reset the upper limit to only open 3/4's of the way. Then
activate the door and see if you are getting the same torquing as when the
door is in a more raised position.
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