Some of the most common problems with solar panels include loose wiring, oxidation, corrosion, system overheat and terminal burn out. However, all these problems cause nearly the only consequence, which is All of these problems cause a decrease in the amount of light solar panels produce.
If you have several solar panels in your home, determine which ones don't function properly by doing a shading test. Use a pillow-sized item to cover a part of each solar panel, testing them one at a time. After some time, look to see if the panel is producing less light than it usually does. If the amount of light decreased, the panel works correctly. If it didn't, there is a problem with it.
Problems with wiring are the most common ones. Take a wiring diagram, and examine all the connections in the system. If everything is connected properly, inspect the system for loose connections, corrosion or oxidation. Tighten the loose wires, take out the wires that have oxidation on them, and install new parts instead.
The system may overheat during the hottest and sunniest parts of the day. If the system produces less energy during the sunniest parts of the day, this is probably why. Inspect the wires and their connections, and repair any poor connections. If you find that some of the wires are very small, replace them with the heaviest wires that are compatible with the system.