Mine was dead, too. So, I set aside a day, removed the entire dash, split 
the air box (it had clips, not welds), then tested the fan directly from the 
battery. It was bunged up! A few spins by hand, some cleaning, and it's 
still going. The fan switch was also bad; that may be a good place to start. 
My switch was welded off inside; I scraped the bad plastic out of the way 
with knoves, chisels, etc. (carving tools, actually), bent the contacts into 
what seemed right, and _it's_ still working, too. The dash looks 
challenging, but slow steady work did the job. I now feel pretty good about 
what's under there, and I took the opportunity to clean, tighten, and 
straighten wires, heater cables, and ducts. It did take most of a day, 
though.      -ed

(82 Diesel Vanagon, 84 Westy)