Chamberlain 3900PLD Home Security System User Manual


 
24
Having a Problem? (Continued)
11. The operator motor hums briefly, then won't work:
The door springs may be broken. See above.
12. The operator won't operate due to power failure:
Use the emergency release handle to disconnect the
door. The door can be opened and closed manually.
When power is restored, pull manual release a second
time.
If a Standby Power Unit is connected, the operator
should be able to operate up to 20 times without
power.
13. Door loses limits.
Collar not tightened securely. Tighten collar
(see Assembly Steps 1 and 2) and reprogram limits
(see Adjustment Step 1).
14. The operator moves when the door is in operation:
Some minor movement is normal for this product. If it
is excessive the collar will wear prematurely.
Check to make sure the torsion bar is not moving left/
right excessively.
Check to make sure the torsion bar is not visibly
moving up and down as it rotates.
Check that the operator is mounted at a right angle to
the jackshaft. If not, move the position of the mounting
bracket.