Question for everyone, in the Vintage Motorcars Speedsters, what are all the knobs/controls? And more importantly, why is there an extra knob next to the parking brake?
As you pull 'up' on the lever, it pulls a cable attached to the flaps in the heater boxes on each side of the engine (exhaust pipes from #2 & #3 cylinders travel through these heater boxes). When you pull the lever, which pulls & raises the flaps, the flaps redirect a portion of the air flow from the fan (spun by the belt pulley on the alternator) to the passenger cabin through vents at both sides of the footwell as well as defrost vents by windshield. Volume of heated air to passenger compartment depends on engine RPM. Higher RPM, more air volume (such as it is).
Lever in 'up' down position = heat to passenger compartment off. Lever in 'up' position = heat to passenger and windshield defrost vents on.