Regards, I already got the diagram, it is the PCB of a Samsung mini split. and the diode also has its DataSheet, it is the same ST02D-200, the problem is that they are 2 diodes in one, one Zener and another Rectifier together connected by their cathodes, the ends are the anodes of both, obviously they cannot be tested with multimeter due to its configuration, and that is what I want to know, how to know if it is good or bad.