This guide provides field-tested troubleshooting procedures for the six most frequent solar combiner box failures, from circuit breaker nuisance tripping to terminal overheating and water ingress. Learn how to detect and fix it. Failure can. When a solar combiner box fails in the field, revenue stops. Understanding the Basics of a DC Combiner Box PV Before we jump into troubleshooting, let's quickly go over what a DC combiner box PV does. Sometimes, minor errors can arise and cause the solar panel to stop functioning properly. Although it might be challenging to.