There is one more part of the circuit you haven't replaced.  Packed into the back of the temperature gage is another integrated circuit (chip and other components).  It can go out too.  The temp. gage can be replaced.  That will probably cure the problem.  The last one I installed worked fine for about 6 months.  Then it quit again.  I haven't had the time to order and install another, but will do that one day.

There may be another problem that is causing the temp. chip to go out.  Voltage surges may be occuring in the 10v regulator circuit.  VW put out an upgrade requireing that a diode be installed in the 10v regulator circuit to stop the regulator from blowing out.  I have a copy some place.   Anyone have any ideas on this?

George