Got my dad’s 3.6 town and country. I live in MN. Coolant level is fine. Has 203f thermostat. I noticed temp gauge seemed low and DIC says coolant was 175f after 20 min of driving. Vent temp felt fine. I idled in driveway for 10 min and temp went to 194f. Drove around and it went back to 175. Dodge website says that’s normal. Only an issue if it throws code. A number of TNC website folks agree. 175 is normal. Is it?
One guy said new thermostat resulted in same 175f results.
And, in summer it should range from 200-210f even on highway. Which I agree it does.
On many/most vehicles, the thermostat is rated at 192 degrees Fahrenheit . . . 
Maybe you should just replace it with a new thermostat of the correct temperature rating, as a first step
In any case, what you’re describing sounds like a bad thermostat, imo
What year is this Dodge van?