The relay for the coolant level light is located above the fuse panel and
sits just about on top of the driver side fresh air intake duct.  If you
reach you hand up there you can just feel it (there are two or three relays
up there).This was the problem on my 85 Westy, changed out the coolant level
sender in the tank and them found the trouble to be the relay.
Hope this helps.

Bill Lund