A mobile environment-controlled unit comprising: a chassis ; a compartment supported by the chassis; and an environmental-control system supported by the chassis and in environmental communication with the compartment, the environmental-control system being configured to control an environmental parameter of the compartment, the environmental-control system including a multiphase alternator powered by an internal combustion engine and configured to supply electrical power for the environmental-control system, the alternator having phase windings and a neutral point for the phase windings ; and a high-resistance resistor electrically coupling the neutral point for the phase windings to the chassis ; characterized in that the environmental-control system further includes a solid-state module electrically coupling the neutral point for the phase windings to the chassis , the solid-state module being configured to monitor a voltage across the high-resistance resistor from the neutral point to the chassis , and to provide an output when the monitored voltage indicates a possible phase-to-chassis fault, wherein the high-resistance resistor has a value in a range sufficient to limit current in a possible phase-to-chassis fault and to dissipate parasitic current during a possible intermittent phase-to-chassis fault. a chassis ; a compartment supported by the chassis; and an environmental-control system supported by the chassis and in environmental communication with the compartment, the environmental-control system being configured to control an environmental parameter of the compartment, the environmental-control system including a multiphase alternator powered by an internal combustion engine and configured to supply electrical power for the environmental-control system, the alternator having phase windings and a neutral point for the phase windings ; and a high-resistance resistor electrically coupling the neutral point for the phase windings to the chassis ; characterized in that the environmental-control system further includes a solid-state module electrically coupling the neutral point for the phase windings to the chassis , the solid-state module being configured to monitor a voltage across the high-resistance resistor from the neutral point to the chassis , and to provide an output when the monitored voltage indicates a possible phase-to-chassis fault, wherein the high-resistance resistor has a value in a range sufficient to limit current in a possible phase-to-chassis fault and to dissipate parasitic current during a possible intermittent phase-to-chassis fault. a multiphase alternator powered by an internal combustion engine and configured to supply electrical power for the environmental-control system, the alternator having phase windings and a neutral point for the phase windings ; and a high-resistance resistor electrically coupling the neutral point for the phase windings to the chassis ; characterized in that the environmental-control system further includes a solid-state module electrically coupling the neutral point for the phase windings to the chassis , the solid-state module being configured to monitor a voltage across the high-resistance resistor from the neutral point to the chassis , and to provide an output when the monitored voltage indicates a possible phase-to-chassis fault, wherein the high-resistance resistor has a value in a range sufficient to limit current in a possible phase-to-chassis fault and to dissipate parasitic current during a possible intermittent phase-to-chassis fault. <EOS>