flakey temp guage

i have a 89 taurus with a 3.8 and it runs good, i had the car for more then 4 years now and my temp guage sometimes goes just a little past the halfway mark but only in the summertime when its above 65 outside. i replaced the ect senser,pcm. everything else works fine concerning the cooling system. i did hook a togal switch up to the ect senser so now if i want i can turn the cooling fan on from inside the car so when im city driving i can turn the fan on and then the temp guage stays at quarter mark. i talk to other people about this and everybody seems to have a different opinion about where the temp guage should stay on a taurus. does anyone else have the same probelm?