1987 Vanagon GL Syncro tin-top.  Overhead controls and ductwork, A/C system.
1. Fan speed "3" does not work.  Everything is still on, just no fan.  "1", "2" and "4" fan speeds work.        Where do I start looking for this problem?
2. When I switch fan speed to "4", I start getting a burning smell from the vents.  When I go back down to "1" or "2", smell eventually goes away and runs fine all day long.        I opened the driver side A/C rear panel and see/smell no burnt items among the wires and relays.  Do you think this smell is coming from the evaporator coil area or the control knob area in front?

Thanks.
-Dick-