A system includes a circuit interruption device, such as a circuit breaker, contactor or other switch of an automatic transfer switch (ATS) or a similar device providing power to an input of an ATS, and a monitoring circuit, such as a controller of the ATS, coupled to the circuit interruption device and configured to monitor voltages at inputs and outputs of the circuit interruption device, to monitor an auxiliary contact signal associated with auxiliary contacts of the circuit interruption device, and to determine a status of the auxiliary contacts responsive to the monitored voltages and auxiliary contact signal.