A tester for a default mode of operation of an alternator is provided. The tester includes an internal memory having computer executable instructions and a processor coupled to the internal memory and to an alternator via a communication bus. The processor is configured to execute the computer executable instructions in the internal memory to provide at least one parameter associated with a vehicle to the alternator simulated as a communication signal over the communication bus, detect an absence of the communication signal at the alternator, test, upon detecting the absence of the communication signal, whether or not the alternator enters a default mode of operation, the default mode being indicated by a preset output voltage uniquely associated with the default mode and monitored by the processor, and indicate whether the alternator entered the default mode successfully.