5kcst thermo sensor Q

[Steve Sherman]

I'm still trying to track down my "overheating" issue with my 87 5KTQW,
and started thinking about a new line of investigation...  Perhaps my
engine is not overheating (it never gets real hot) but rather it is a
sensor issue.

The symptoms I see are temp gauge running at 3/4 level, and when stuck
in traffic on hot days, or going slowly up a steep hill on hot days, the
flashing triangle with a thermometer will come on in the dash.  I was
wondering what sensor(s) run the dash temp gauge and set off the temp
warning symbol?  are they the same one?  Perhaps I should replace it?

TIA