Our example system was producing about half of its rated power. What could have gone wrong in this situation? Let’s say no shading or error codes were observed, and, from the ground, no damage was visible on the face of the array. However, a rooftop inspection revealed a loose connection between two modules where a connector had come undone, and testing showed one series string with open-circuit voltage close to our expected value and the other one at close to zero. Not surprisingly, the modules with the loose connector were on the low-voltage series string. Perhaps the connector was not completely closed to begin with, and the module wiring was pretty taut underneath the array. Expansion and contraction within the rack and modules might have been enough to pull this connector loose over time. The connector will need to be carefully inspected and, probably, replaced, since there’s likely to be heat damage from the long-term loose connection.