As a critical electrical device on the DC side of photovoltaic systems, solar combiner boxes are susceptible to various types of faults, which are often interrelated. Here, we list the 10 most common problems, analyze their primary causes, and provide detailed diagnostic and resolution steps. Learn how to detect and fix it. The solar combiner box, also known as a PV string combiner box, centralizes and protects your PV array wiring. Follow the troubleshooting methods below if an unforeseen communication failure occurs: Verify that the host computer. The pv combiner box serves as a critical component in photovoltaic systems, consolidating multiple DC inputs from solar panel strings into a single output that feeds into the inverter.