About one month ago on a whim, I decided to see what would happen if I pulled up on the heater lever in my '73. I'm talking about the lever on the center tunnel right next to the hand throttle.

It worked fine and then I returned it to the down position. One problem however: I have noticed hot air coming into the cabin through a vent located right above my feet on the driver's side. I put my car on a lift to confirm that the cable connected to the flaps on the heat exchangers had not broken. In fact, both flaps are in the open position (with the holes wide open), so I shouldn't be getting heat in the cabin, right?

Unfortunately, on the driver's side only I'm still getting this continuous hot air and it is annoying the sh*t out of me (especially here in Orange County where it was 80 degrees today )!

Any ideas out there if there is something else that regulates air flow into the cabin that I should be checking. Many thanks in advance!!