Opener works for one second, then auto-reverses for one second

Very strange (to me) problem; I'm hoping someone can offer any clues as to what is going on.

Short version:
My Craftsman 139.53414SR garage door opener will lift the garage door for about one second, then auto-reverse for one second. When the power head is removed from the track and chain, the same issue still exists: one second in one direction, auto-reverses for one second in the other direction.

Long version:
Unnoticed by me, the ceiling support hangers installed 26 years ago had started to bend. This ultimately ended up with the chain sprocket being sheared off. I purchased a replacement kit, removed the track and power head from the bent hangers and took the power head off the track. Opened it up, removed the old gear assembly, cleaned everything up and installed the new gear assembly, greasing appropriately. Re-connected the power head to the track and chain. Tested the opener several times and it moved the carriage smoothly for the appropriate length of the track. Re-installed the track and power head on the new ceiling hangers. Tested operation and adjusted the up and down movement so that the door opened up until even with the bottom of the top door frame and lowered until just touching the floor. Cleaned up all the tool, patted myself on the back for a job well done and went inside for a late lunch.

Came out an hour later to take the recycle bin out to the street and pushed the wired button to open the garage door. It went up a foot, then auto-reversed back down. No matter how many times I pushed the wired wall button or the wireless remote, the door would go up a foot, then down a foot. Somehow, with all the presses of buttons, the door ended up about two feet up in the air, but still going up a foot, then back down a foot.

Uninstalled the power head and opened it up. Checked the adjustment screws and contacts on the limiter board and they appear fine. Disconnected the limiter board completely; didn't help.  Adjusted the Force Up and Force Down buttons to see if that would make a difference. Nope. Loosened and tightened all the screws to the metal chassis. Didn't help. Reaching for any possible solution, I even changed the light bulb; no change.

I'm guessing the issue is with something on the circuit board, but really don't have a clue. And, of course, the opener worked fine for the 10 or 15 times I tested it before letting it sit for an hour.

Any tips, clues, hints or advice related to this problem welcome!!

Full Size Photos at
http://windinthetree.com/IMG_1541.jpg
and
http://windinthetree.com/IMG_1542.jpg

Thanks

It sounds like an RPM Sensor problem. Check & make sure the wires are plugged into the sensor board. Also make sure the interruptor cup is spinning through the "U" shaped sensor on the sensor board. If that all looks okay then it's possible that the RPM Sensor itself has failed and needs replaced.

GDZone wrote:It sounds like an RPM Sensor problem. Check & make sure the wires are plugged into the sensor board. Also make sure the interruptor cup is spinning through the "U" shaped sensor on the sensor board. If that all looks okay then it's possible that the RPM Sensor itself has failed and needs replaced.

Thanks for the reply and the guidance.

The plug is definitely engaged firmly onto the pins and the interrupter cup is spinning freely through the black sensor. I'm happy to replace the small board; any suggestions as to where I might go online to do so?

Just do a Google search for "41C4398A RPM Sensor" and you'll find plenty of places to purchase it. I don't know if that's the correct one for your operator but it's the most common one for Sears/Craftsman/Liftmaster/Chamberlain operators.

GDZone wrote:Just do a Google search for "41C4398A RPM Sensor" and you'll find plenty of places to purchase it. I don't know if that's the correct one for your operator but it's the most common one for Sears/Craftsman/Liftmaster/Chamberlain operators.

Searched and ordered for $11.

Also found a YouTube video that says you need a new RPM Sensor Board "if your door opens six inches then automatically closes six inches". Bingo!

I will update after the new sensor board arrives, most likely the beginning of next week.

Update:

The new RPM sensor arrived and was immediately installed. The power head of the opener now works fine. Yay! A few minutes of re-attaching the power head back to the ceiling hangers and a few adjustments to the up and down and we're back in business.

Thanks very much for the help.

Ladd

Good to hear it. Glad we could help.