Hi Volks,
    I have been working with a friend and fellow listee Kay Fremgen on his
87 westy van with ac and at  that has every symptom of a thermostat that
opens too late. The instrument cluster gauge is functioning correctly and
shows a higher reading than normal operation (1/2 way between the led and
hot). The thermostat seems to be opening about 10 C degrees too late thus
the engine coolant loop seems to be a little too hot. I have tried three
different 87 degree  thermostats the last one I pulled from a van that
functioned correctly.  The left and right  hoses at the thermostat housing
are 10 degrees hotter than a normal van (one the has the temperature gauge
sitting  at the led).  After circulation begins the radiator gets hot and
the fan goes on and off at the correct radiator temperatures. I am stumped
and looking for some fresh ideas. tia
Darrell

Ps. I am not only relying on the van gauges I have verified the reading and
temperatures with a temperature probe.