GARAGE DOOR OPEN PARTIALLY THEN CLOSES

[rbm328]

I have two garage doors. One works fine, other side opens partially then closes. After looking closely, one that opens partially has excess cable - about 6" worth (on each side of door) . I can't believe BOTH cables for door stretched THAT much. Where did excess cable come from?
Thoughts?
Is there a spring that assists the lifting? or is it all done by the motor?
1st pic is left side of door, 2nd is right side of door, 3rd is normal other door-RT side.

 

[Snoonyb]

This should be done by a professional, not that you should not watch and learn.

The spool that the cable winds up on has come loose and needs to be retensioned, which will take the slack out of the cable, as well as increase the spring tension in assisting the operator operation.

 

[rbm328]

i will definitely let a pro do it. i was trying to calculate the $$$ to get it repaired.
it doesn't sound like a major repair though

 

[Snoonyb]

It shouldn't be and when you see it done, and the precautions taken, you'll understand the potential danger.