Yep, indeed you may find you'll need to pull the dash. The Behr unit I
have has 3 switches. 2 are identical and control the fan speed and
whether it is on or off (there are two fans). The other switch controls
the AC temperature. This is not too dissimilar from later AC systems,
except that the 2 fans are separately controlled (later Vanagon AC
units, run the 2 fans in parallel and only use a single switch.)