Abstract: A roller drive mechanism for an automotive HVAC film valve belt includes a single motor type drive that automatically compensates for continually differing belt wind up and wind off rates, while maintaining at least a minimal belt tension, and without the necessity for precise adjustment. A central motor drive shaft is split between a fixed end and a yieldable, slidable end. The two ends can turn at the same rate from the single motor, but the ability of the second end to slide back and forth allows one roller to match its belt handling rate to the other roller automatically, while the always stretched spring maintains a certain minimum belt tension, while also accommodating adjustment tolerances.