[Rick Becker]

I just checked the manual, where the valves are called air gates. If the cable breaks (or is missing), the air gates are designed to block air from traveling inside the car, and instead release the heated air back outside thru the four openings you see under the car. So unless the gates are stuck open (letting air inside) right now, if you install a new cable you should be getting a lot more warm air inside this winter.