In a vehicle air conditioner, an air conditioning case has a front air passage and a rear air passage through which air is blown to a front seat side and a rear seat side in a passenger compartment, respectively. The method further includes determining a diagnostic parameter indicative of a fault of the electrical machine based on the measured operating parameter. A carrier-removing roller to which bias can be applied abuts the intermediate transfer member so as to remove a carrier while packing softened toner by the force of an electric field induced by bias.