I've said the some similar things about replacing fuses, but I believe that some people will find a way to rationalize this behavior.
  If you're on a long trip, it can "get you there", but as a regular repair, it's not the way to continue.  
  The added load from a 'dying' component creates excess current draw in the entire circuit. This will either blow the fuse, melt the contacts on the switch, or both (especially if you just keep replacing the blown fuses).
  Installing a larger-sized fuse, just makes the circuit fail elsewhere.  If you're lucky, the switch plastic melts and opens the circuit, shutting the unit down.  If you're unlucky, the wire gets so hot that it melts the insulation, shorts to another conductor inside the harness, possibly blowing some other component, like your ECU. Or even worse, starts something burning.  
  It seems clear to me, that the best course of action here, is to repair (lube?) or replace the blower motor. Even if it is a PITA job....

Mike B.  
  ----- Original Message ----- 
  From: Dennis Haynes 
  To: vanagon@GERRY.VANAGON.COM 
  Sent: Tuesday, December 29, 2009 10:00 AM
  Subject: Re: question regarding front heater switch and knob, 1990 Vanagon GL

  Sure sign the blower motor is about to seize of otherwise fail. Fuses should
  never just be replaced without the cause being determined and corrected.
  Also, as I have written in the past there is no real reason or benefit to
  operate the dash heater fan on that high speed. The interior will warm
  faster along with the windshield defrosting with the fan on speed 2. Once
  moving on the highway turn it off to save it.

  Dennis

  -----Original Message-----
  From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
  Woody Halsey
  Sent: Tuesday, December 29, 2009 8:03 AM
  To: vanagon@GERRY.VANAGON.COM
  Subject: Re: question regarding front heater switch and knob, 1990 Vanagon
  GL

  It's interesting that David comments on that circuit being overloaded. I
  find that fuse brined out pretty regularly! Just replaced it again
  yesterday.

  Woody
  83.5 V'gon
  Haverhill, MA

  -----Original Message-----
  From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
  Of David Beierl
  Sent: Monday, December 28, 2009 2:27 PM
  To: vanagon@GERRY.VANAGON.COM
  Subject: Re: question regarding front heater switch and knob, 1990
  Vanagon GL

  At 07:43 PM 12/27/2009, David Cohen wrote:
  >  The switch keeps sticking  in the
  >third position.   Where do you recommend I buy a switch  from?

  That's because the switch body is thermoplastic; it softened and the
  contact pressure drove the hot contact down into the switch body.  On
  a desert island you'd find a way to fix it.  Bus Depot, Van-Again, no
  doubt others have new;  Chris Turner <jordanvw@aol.com> no doubt has
  used ones -- if used, try to get one from a rear blower, they're the
  same switch but less load on them.  But if you add a relay for the
  high speed you shouldn't have any further switch problems.  On the
  1.9l the circuit is overloaded but the 2.1l don't need a new circuit,
  I think, just getting the load off the switch; so you can take the 30
  terminal off the switch supply, cut and use the high-speed wire from
  the switch for the 85 terminal; 86 to ground and the other one to the
  fan high-speed wire.

  Yrs,
  David