i have a craftsman garage door opener, approximately 17 years old. i've noticed the chain is sagging and the door only opens up 1/2 way due to it getting stuck or caught on something - can anyone help with this problem? we've had the springs replaced and that doesn't seem to be the problem, just the sagging chain.
There should be an adjuster which lets you take the wear slack out of the chain/cable. On my Crapsman openers it's built into the traveling carriage to which the door arm attaches.
Look for it, and do what it takes to tighten up the chain a bit.
HTH,
Jeff
With the door disconnected from the opener (no load) there should be approx 1/2" of sag in the chain.
As usual, the first thing to try is to disconnect the door & open the door by hand to see if it opens easily & freely. If it doesn't look for something catching the door by the track (like broom handle, etc or the door lock partially engaged. If it does move freely run the opener w/ the door still disconnected to see if it stops without any load.
Does it open exactly half way or is it stopping where the rail is spliced together (usually 1/3 & 2/3). If it's stopping at the splice bend the four taps up slightly on the inner carriage (part that door arm connects to). These tend to catch on the splice, but don't bend them up to much or the outer carriage part won't go past them to re- connect the door.
Inspect the the shaft & the motor head sprocket on top of the unit that the chain goes around. The sprocket is welded to the shaft & they have been known to separate from the shaft & they bend upward until they break completely. Also make sure that the shaft is pointing straight up & down. If it appears that it is leaning toward the door the bearing that the shaft is going through is probably worn out. This is another known problem & over-tightening the chain or a heavy door will make the problem occur even sooner then normal. This part is an assembly that includes the shaft, chain sprocket, bearing plate, & plastic drive gear, but does not include the limit gear sprocket at the bottom of the shaft. After you remove the limit gear & the 3 screws holding the bearing to the motor head the whole assembly lifts out from the top. If you remove the chain do not move it until you put it back on the sprocket & put it back as close to the spot as possible. If you move it to much or run the opener without the chain, you will have a heck of a time getting the limits reset. Also please note that the 3 screws holding the bearing plate are a metric size.
Yes there is a threaded rod on the chain to tighten it, but only tighten the chain in this manner after you have verified that there isn't something else causing the chain to sag.
DoorDoc
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