There is a lot of information on the vanagon fan motorsystem.    Ken at Vanagain and Go Westyhave some good postings to trouble shoot as well as the archives.   I would like to try to fill in some of theblank space in the trouble shooting area.  

    I have 87 westywith AC that is very much like the 86 westy, the fan motor system on the olderand newer vanagon are only slightly different.  I am not sure why but the Bentley manual does not show the resistor inthe electronic diagram.  

   My low speed fanwas not going on.    Following Ken atVanagain protocol I jumpered the sensor and nothing happened.   Ken does not indicate what to do in thissituation.   I should add that the fandid not come on when I turned on the AC.  Baffled, I wasted a lot of time looking at the wrong things.   A situation like this you should look againat the 30 amp fuse and check that fuse time to time as you trouble shoot.   At this point you should drop the spare tireand use an external power source to confirm that the motor itself is notbad.   It is unlikely to be bad.    When I looked at the motor what I saw werethree wires.   The medium size groundbrown wire, the medium size red low speed wire and the massive red high speedwire.   What were the Germans smokingwhen they made the ground wire smaller than the power wire?   To confirm the ground wire problem I pulledthe resistor connector behind the headlight and applied 12 volts to the mediumred wire that goes to the fan motor with Ken’s jumper protocol  and confirmed that the fan motor did not comeon.   I then jumpered the brown groundterminal to various locations near the fan motor with (Ken’s protocol jumpersetup) and the red wire from the resistor energized and found a good ground andthe fan came on.   My final location fora new 12 gauge ground wire was the horn bracket attachment to the frame.   The newer style fan motors have a screwattachment for the wires.   Not sure whatis the best way to add the ground wire for the older style clip arrangement.

   Looking back at thelast summer I can recall that I must have had an intermittent ground problembefore the acute failure.   There weretimes when the temperature gauge read higher than it usual.   I would suggest any one who has not added asecond ground wire consider doing this the next time they go to check theirspare.   It is not something you want tomess with on the road on the hottest day of the year.