Well, it went to zero amps when I covered the panel, but, when I uncovered the panel, it didn't come back, and I started thinking about my system- 24V battery, with a Tracer AN 20A solar controller, and I just took, at best, my solar input voltage from about 34 to about 17. So, I guess I proved nothing about diodes, but, may have gained some useful information about the Tracer's behavior- it went literally to zero and the solar power indication was gone, but before I came in to write this (after a couple of minutes staring at it), it was indicating solar charging, and a couple of milliamps. Perhaps the computer in the Tracer will sort things out in time.