Electrical problem
2003 Chrysler Town and Country 6 cyl Two Wheel Drive Automatic 70000 miles

The heating/air conditioning fan is stuck on high. attempts to adjust the speed and even the various options for direction of flow (e.g. defrost, floor, or vents) doesn't work. After several months, the fan no longer works at all. The temperature was adjustable, but the fan speed was not. So we could turn on the air conditioner on, or turn it off and raise the temperature to get heat. Now the entire system will no longer turn on or off. Any ideas what part I would need to replace to fix this issue? Thank you!