I seem to have a recurring problem on my 87gl.  The heater control will not
completely shut of the hot water flow to the heater core.  I sure don't
need this in 90+ hot weather.  About two years ago I had my mechanic
replace the valve and it was fine till recently.  Has anyone else run into
this and if so is there a more long term fix than replacing the valve every
couple of years?  As I remember the mechanic had a miserable time getting
the thing replaced.

Dave