On my 87 Westy, I seem to have the 'hot foot syndome.' It seems
something is stuck open so the outside air is let in through the
footwell regardless of the levels' adjustment. I have replaced the
heater valve with much pain, but the problem persists. Symptoms are:

I can feel the draft on my foot always with the footwell vent closed
when the car is moving.
On hot days with the A/C on it is almost unbearably hot.
On cold days it blows cold even with the heater valve fully open. When
I open the heater valve It mixes with the hot air from the heater
gives me lukewarm heat.
When I am not moving I do not feel the draft so the hot air subsides
in the summer (unless the fan is in the crazy high speed mode with the
A/C on) and the cold air subsides and I can feel the fully heated air
in the winter.
No heated air ever comes out from the windshield defroster. (This may
be a critical clue). It is always ambient temperature.

I am fairly sure it is the seal deteriorating or some debris stuck in
the air-distribution box. My question is, will I have to remove the
dash to solve this problem or are there other remedies?

Thanks,

Jean-Woo Kim