My 88 Vanagon has a slightly different temp warning light problem.  If I start a cold engine the light goes out after 3-4 secs. as it should and it never comes on again no matter how far I drive.  However, if I restart an even slightly warm engine the light keeps flashing while the gauge indicates normal temperture.  It is otherwise running fine, the coolant level is good, and the V-belt seems good.  Any syggestions
          Tom