I have a dozen of the O-27 ones, if that's what you have (versus full 'O', which I know they also come in).
The common problem that I have had maybe 6 times now is a problem caused by a worn (the nub wore down) or defective limit switch. I have NOT been able to find a source for replacements though.
For me, all but one I fixed the same way: the little arm on top was not depressing the limit switch plunger enough for the electronics to realize that the switch had been switched, even though it was.
Gunrunnerjohn actually jumped into my thread here, many years ago now, with a suggestion on how to fix the issue with JB Weld. I tried that but it didn't work FOR ME. Might for you.
What has worked for me on each one is to wrap a thin strip of tape around the arm on top at the correct spot. what happened in my case is that little nub on the end of the arm wore down and the 'brown part' that swings to depress it was not able to depress the plunger enough.
Here are some comments from those early on threads that I saved - you may find them useful:
FIXING THE MICRO SWITCH – A REPLACEMENT PARTThe mirco switch is identical to the one is Lionel’s Fastrac switches. I was sent one in November, 2012 as a test. It was a perfect replacement. The Lionel part number is 610-2045-351. It might be called a ‘cherry switch’ on their site.
COMMENTS FROM OGR FORUM
(my comment on one of the threads): DO you see that little 'nub' on the end of the 'arm' - that's what is wearing away on mine. On the 3 that went bad that 'nub' no longer is there. I compared it to a good switch and the good ones have the 'nub'.
JB-Weld is your friend if the nub is gone. Just build a new one with it, great stuff!
That inside K-Line motor picture and mechanical layout looks exactly the same as inside a Z Stuff actuator for Ross turnouts! In fact, the circuitry of K-Line and Z Stuff appear identical when I traced them out several years ago. Not to start a thread flame war here, but wonder who "borrowed" what technology from whom???