A supplemental circuit board is provided for a furnace and air conditioning system to power the blower motor so that there is normal heat speed during a heat cycle, and normal, full speed when there is a normal cooling cycle. When there is a call for economy, dehumidification, or partial speed cooling, an inverter provides pulsating power for efficient reduced blower speed operation. An actuator circuit provides a blower-motor in-use signal, and a low-speed logic circuit provides a low-speed signal when there is a call for reduced speed cooling. In case of circuit failure, the arrangement defaults to normal speed operation.