My tempature gauge needle had been south of the LED light by about 1 needle
width for more than a year. This pheonomena had occured suddenly, and I
accepted that my engine was operating correctly despite this(after much
fretting).Recently, the coolant level sensor blew out of it's hole in the
expansion tank.I replaced it with a sensor that I had kept for a spare. Lo
and behold, this new- used sensor corrected  the temmp gauge problem , and
the needle is happily back where it belongs(right over the LED).Would you
believe me if I told you that I knew this would happen and that I was only
trying to get more miles out of the old sensor?That this repair was not the
result of random trial and error,but of vast mechanical know how.Wish I
could claim that.
Closer examination of the old sensor showed cracks in the plastic where the
plastic covers the metal sensor probes.Perhaps the cracks were allowing
a "short circut",making for an incorrect reading somehow?!??$#@.Whatever,
replacement of this sensor just hapened to correct this problem for
me.Maybe it could help your situation.