It wasn't until I got my 3rd vanagon that I discovered how to
distinguish the heater control levers without looking at them.

When I bought my '91 I noticed that the 2nd and 4th levers have bumps on
the sides of the knobs.  These control the hot water to the heater core
and the fresh air to the ceiling vents toward the back.  Since I still
had my '84 at the time, I went back and checked it and found similar
bumps, but much smaller so I had never noticed them.

Larry A.