A 5-year-old 360W rooftop off-grid PV power station had worked on the roof of a house in Mirpur, Dhaka. There were 36 photovoltaic modules of 10W each. The modules were not cleaned for the past six months and were visually observed due to dust and bird droppings. After that, all the modules were cleaned and visually tested using a standard camera. This time, the results showed discoloration, corrosion, cracks, and delamination. Two further types of investigation were done here. One was an image-based investigation with a thermal camera, and another was electrical characteristics through a professional PV analyzer. First of all, PV modules were tested one by one using a thermal camera, and hotspots were observed in one or more cells of some modules. Finally, each module's voltage-current power and IV curves were determined by a PROVA 1011 PV analyzer. These results found that modules with more fault detection had lower output power, and modules with hotspots in multiple cells also had lower output power.