The primary focus of this paper is the reliability / failure evaluation of a 26-year-old photovoltaic (PV) monocrystalline silicon (c-Si) system located in Phoenix, Arizona (a hot-dry desert condition). This 4000-frameless-module bipolar system was originally installed in August 1985 with a rated capacity of 175 kW (17° fixed south tilt). This paper presents only the degradation and failure modes, and the degradation rate and its determination of this power plant is presented in another/twin paper of this conference. The results obtained from the extensive visual inspections and other non-intrusive tests made on the entire plant were used to determine the degradation and wear-out failure modes. The encapsualnt browning, cell gridline blossoming, cell-ribbon solder bond degradation, ribbon/metal-strip (copper) attachment degradation/break outside the modules, cell cracks and backsheet delamination have been determined to be the degradation and/or wear-out failure modes of these 26 years old modules in this specific hot-dry desert climate.