> The sensor is on the flange that is pointed to the front of the van, it has
> the small heater hose connected to it. The temp sensor on the upper
> radiator hose flange on the side of the head is for the temperature gauge.
> They are both the same if you want to switch them to test it. The relay
> goes into full glow when resistance is high, disconnected is very high
> resistance and full glow should be in the area of 30 seconds. The relay
> like to get very corroded in the location it's in so pull it out and look
> at the terminals. Good luck.

Not sure about the Vanagon diesels, but on the Golf/Jettas, a common 
failure mode for this relay is to emit a buzzing/clicking sound as 
the corroded contacts try to make the connection. I've had two of 
them do this on my Jetta. Relay is about $45-50 from FLAPS, more from 
dealer. I got 2 of them from an auto wrecker for $10 along with some 
other stuff. 
Shawn & Janis Wright
'88 Westy (336k) '85 Jetta TD (361k)
VWnut@smus.bc.ca (swright@smus.bc.ca)
http://www.islandnet.com/~swright/vw.html