Most likely cause is a failed engine thermostat.
Temperature gauge may drop when heater turned on because additional coolant from heater core is introduced to cooling system - usually this coolant is cooler than what is currently circulating
Over temperature warning.
yes it can
Engine is overheating, faulty gauge, faulty temp sensor......
A short between the heater switch and temperature gauge.
In the middle (about 195 degrees).
Thermostat probably needs to be replaced.
Turn on your vehicle's heater
I very much doubt it.
It's most likely the sending unit. have your mech check that for you.
Broken thermostat. Common Chrysler problem. Replace the thermostat.
My Altima had that problem and it was the water pump going out. It started with temperature gauge was moving, but then it started leaking and finally the heater stopped being warm at idle.