The fact is, solar energy systems are very reliable. So reliable that not much is said about what can go wrong. Well, nothing can go wrong…can it? Granted solar panels have no moving parts so there is little that can go wrong. There are no gears to be broken or belts to be torn. Nonetheless, they are not infallible. On the other hand, if your system stops working to its full potential, there is no need to look up emergency numbers in the phone book or to start spreading profanities and lamentations all over the neighborhood. There are a few problems that can arise and subsequently a few ways to troubleshoot them.
The first thing to do if you notice a decrease in system output is to locate the problem. You can do this with a technique known as a selective shading test (first make sure your system is not already being shaded). Shading has a profound effect on conventional, photovoltaic panels. Even shading one corner of the panel can decrease output up to 50%. Therefore, a good way to locate a malfunctioning panel is to go down the row of panels shading a small portion of each in turn. With each panel you should see a noticeable difference in system. When, after shading a panel (a pillow or large hat will do) you fail to see a difference, you have found the guilty panel.
Perhaps 90 percent of the time, panel malfunction revolves around wiring: a loose connection here, corrosion or oxidation there. Heat fade is another possible source of trouble, which occurs when the system does not work as well when the sun is hottest. It is usually caused by poor connections or undersized wiring. Throwing water on the panels to cool them down, while monitoring current fluctuations is a good way to confirm heat fade. Using the selective shading test will help locate weaker panels where wiring should be repaired or replaced.
Burnt terminals are yet another, and fairly familiar, cause of electrical resistance. Most of us have seen similar corrosion and oxidation on our car batteries. Replacing all metal parts that show signs of oxidation and rewiring should take care of the problem. Burnt terminals are usually the result of too many panels wired into the same circuit. Rewiring some modules on a second circuit is a likely solution.
As you can see, most solar system malfunctions are caused by faulty wiring. It is rarely the system components that fail. Be advised that wiring can be dangerous. Do not attempt any electrical work that you do not feel comfortable with. It is always safer to hire a professional. In addition, be sure to double-check the system warranties. It’s almost guaranteed that you have one or more. Nearly every state requires at least a 2-year warranty on parts and labor and many systems come with 20 year warranties on output. Solar systems are warranted well because they work well. So don’t hesitate to call your installer and let them help you troubleshoot the problem. These problems are usually more like quirks and not difficult to fix.
Source: Troubleshooting a PV Array