I've been looking for a solution to losing my Vanagon's front heater fan
low/med speeds for a couple of months.  As you may know, the resistor
can fail leaving you with only the high speed.  This is great for
defrosting or cabin air exchange, but not so great for heating.

I searched the stock shelves of my local NAPA (great folks who
occasionally let me do stuff like this) and found a heater fan resistor
that resembled the one in my Lancia Scorpion, a series of resistors in a
metal cage NAPA part BR85, $6.95 with my AAA discount.  I experimented
with it in my Scorpion and figured out how to hook it up using the one
fan speed still available.

To solve my Vanagon problem I made an approx. 8" harness of 12g wires
that takes the power that goes to the switch as the high speed, and the
other two speeds as two lower speeds, although you have a total of four
speed options with this part.  The resistor is nestled just to the right
of my stereo/ashtray.  This area seems pretty devoid of other wires etc.
which is important as the resistors do get very hot, glowing actually. 
Normally the resistor is inside the heater fan housing or duct where the
moving air helps keep it cool, so we'll see how it works.  This will
also work in my Scorpion who's resistor is also broken.

The hardest part is deciding which speeds to use, I opted for the upper
3 of the 4, the lowest speed seems pretty useless in the larger volume
of the Vanagon.  Might be good for the Scorpion though.

Gregory Smith
Olympia, WA USA
'88 Vanagon GL
'77 Lancia Scorpion