The door felt fine for the first car and heavy by the second
Why it happens
A spring losing tension doesn't always fail all at once. The door can feel a bit heavier each time, lift crooked or make a new noise. A bang from the garage, or a gap of about two inches in the coils of a torsion spring, means one has already let go.
Why it matters
With two drivers in the house, someone usually notices within the hour. That's a good thing. Springs carry most of the door's weight, and a door that's lost one can drop without warning.
Response
Thom replaces snapped or tired springs. Tell him the door type when you ring, so he brings the right spring. On a two-spring door it's usually worth doing both at once, since they've done the same number of cycles.




