Fixed, at least for now

For a while our garage door opener has been on the decline.  Then this week it stopped working altogether.  When I took off the cover I saw drifts of plastic snow; the main gear had disintegrated.  Why are plastic gears used here?  Not sure if it degraded over time (the opener is over ten years old) or if it happened drastically.

Notice the lack of teeth on the old gear; compare that to the beautiful canines of new gear...

So I found the part on Amazon and received it today.  Took a 1/2 day of vacation to work on it.  Tedious work.  To replace this gear (and the "worm" gear) you pretty much have to take the entire opener apart and reconstruct it from scratch.  So lacking in mechanical skills this was quite a chore for me.  But step by step it eventually came together.  I took some pictures of the guts so I had some clue how to put it back together.  I first used this technique when replacing our furnace blower motor a few years ago.  Invaluable.  However, this time I didn't have to refer back to them.  That's just as well and good to have a keepsake anyway.

So once the reassembly was complete I put the chain back on and tried the opener.  I quickly realized something was not right.  The chain went herky-jerky so I cut the power.  One side of the chain was extremely taut while the other had slack.  I mean, "extremely" in the sense that the drive rail was bending - not good.  Hmm.  Methought there must have been a twist in the chain.  Get Mare to help me take down the chain (with safety goggles now), make sure it is straight.  Put it back, try again, but same problem.  Hmm.  Oh, it must be due to the missing lock washer that I misplaced when taking the chain apart the first time.  I couldn't find the stinking thing so get Elizabeth.  She finds it in, well, about 10 seconds.  I am overjoyed so I pay her bountifully ($1) for her services.  Put on the lock washer, try again, but same problem.  Hmm.

At this point I am quite flummoxed.  But I have not lost my temper, not thrown anything, not snapped at anyone and anything in sight.  This is good.  So it's getting later and we head to town for some supper and errands; all I can talk about is my theories of what is going on.  Based on the tension on the one side I determine the door is trying to continually close itself.  It dawns on me that there must be some obstruction causing the sprocket to turn, but the chain to not move.  So we get home and I head to the garage to prove my theory.  Sure enough there is an obstruction, but then methinks more about this and I realize the opener is set on the "up" contact.  Oh.....  So the opener thinks it is up and tries to go down, but the door is already down so, well, bad things happen.  I manually move the contact gear to the "down" contact and try one more time.  It works!!  Up, down...  Up, down...  Up, down...  This is fun!  I'm still not exactly sure why the safety mechanism didn't kick in when the door was trying to go down when it was already down.  We tested the up and down safety mechanisms and they are working normally.  This may remain a mystery.

I hope the fix lasts for a while.  Nothing like a $15 replacement part for a good DIY project.  Never done much with garage door openers and now I know a whole lot more than I did this morning.  Probably know too much -- I'm thinking it shouldn't have taken me near as long, but oh well, live and learn...