a fan speed controller of an automotive vehicle air conditioning device is usually placed in an air flow duct to be effectively cooled . thus , compact construction of the speed controller is needed to obtain a larger air flow in the air flow duct . for this purpose , various compact resistor units for the speed controller have been proposed . however , some of them are poor in durability against shocks . in view of this , a compact resistor unit for a speed controller includes a resistor block that has a flat resistor , a flat insulating plate and a flat radiation plate which are respectively positioned against one another . the compact resistor unit further includes a holder block of molded plastic on which the resistor block is mounted . the compact resistor unit also includes a plurality of metal terminals partially embedded in the holder block , where the terminals are connected to particular portions of the flat resistor . the compact resistor still further includes metal connecting lugs that are partially embedded in the holder block , and rivets for securing the resistor block to the connecting lugs .