2002 Explorer coolant temperature issue.

[jsl31206]

Hello everyone. Let me start off by giving some background info on the vehicle and problem I am having.

2002 Explorer 4.0l V-6 non Flex Fuel.

Coolant Temp gauge on the dash is not responding at all and the Check Gage Light is on. When the engine is cool the motor will start most of the time. I can let it run and get to normal operational temp and all is well. Good heat come from vents at idle, etc.

Here lies the problem. Once the engine is hot and I shut the engine down, it will crank but not fire until the engine is cool again. After reading these forums and talking to a mechanic buddy, these are the things I have replaced with OEM parts:

1) Thermostat
2) Thermostat housing and seal
3) Engine coolant temperature sensor on thermostat housing (this model only has 1 sensor on top)
4) heater hose

Any ideas or suggestions on what could still be causing this issue? Also, since this problem started the outside temp is not displaying on the dash. Could this be a bad ambient temp sensor or could it be connected somehow to the coolant problem?

Thank you for any ideas or advice.