This work introduces an improved methodology for detecting the fault in the MOSFET switch used in the dual input fault tolerant (DIFT) DC-DC converter for DC microgrid application. The converter uses both photovoltaic (PV) and fuel cell (FC) sources to make sure that power is constantly available to load. DIFT predict the inductor current and compare it with actual inductor current and gives the result whether fault is present in the switch or not. We also use the FIDES method to find the failure rate of all the components under real-world stress situations, such the temperature and humidity changes that occurs all the time in Chennai. Based on FIDES reliability studies, the switch S3 which is prone to failure is found. If the fault switch is S3 with the help of S3R the demand in the load is maintained. This lets the converter keep working without faulted switch and this is how the output voltage is managed. The suggested way to diagnose can find and fix OC fault in the switch in just one switching cycle (20 μs). It can do the same thing for SC faults in four switching cycles (80 μs).