Mitsubishi Repair: 2003 Galant Thermostat Problem, thermostat control, heater core

Question
I have a 2003 Galant that is having issues with the Thermostat control.  It blows both Hot/Cold fine, the problem is adjusting the temps.  I have turned the knob slowly (as suggested by my local mechanic) but it doesnt adjust the temp.  You can turn it from hot to cold and eventually(sometimes as long as 2 days later) it will make a fluttering sound and then adjust to the new temp.  Someone suggested it might be the heater core?  Ideas?  Extremely frustrating when you can't the temperature to adjust to run the defrost or air.

Answer
Cindy,
There is a valve that regulates the amount of coolant that flows through the heater core.  When you set the dial to "Hot", that means lots of coolant enters the heater core.  When set to "Cold", than no coolant enters the heater core.  So if you cannot vary the temperature, then it most likely means that the valve that regulates the coolant flow to the heater core is sticking.  You would want to have a mechanic inspect this for you to determine the absolute cause of this.
Good luck!