Upper AR problem solved (?)

I was testing the Upper Auto-Reverse problem mentioned in the last post when it suddenly went away. I determined that the problem was that only one rail was switching polarity, not the other. Trying to isolate the cause I used the multi-tester on the PM42 connectors, but having forgotten I turned the MT off, touching the connectors caused the DCS100 to short circuit and the PM42 to switch polarity again (at least the indicator light changed). That reset apparently stopped the problem, as the PM42 now works fine again.

I'm putting this into the "monitor" category on the problem log as I don't understand the solution and thus the problem may reoccur. I'm also wondering if this was the same problem I had with that one "bad" PM42 section in 2007. Hmmm....