Ok Listees here is one for ya

       After many hours of diagnosing our blinking temp sensor on our 83.5
     Westy- we have flushed it, replaced thermostat, sensor and water pump
     and replaced rear heater core( it was leaking) I think we finally are
     making some headway. We took it for a 100 mile drive yesterday and
     everything seemed fine. The temp guage was half way to the LED. Once
     we got on the freeway it started goin down. Now its startin to get
     cold here in Ohio but is the temp guage supposed to do this? It went
     down as far as it can go at some points. Is this normal? It would
     start going back up as soon as I got off the freeway to "normal"
     levels. After the trip I looked things over and everyting seemed fine.
     Thats a lot of cold air hitting the front of the van but I cant
     believe that it would register nothing at all. We are using a very
     measured 50/50 solution as well and the coolant level is still where
     it was when we started. Any ideas?

     -Mike