If it shows hot on the gauge and it is not hot, there is a gauge or sensor problem.
That is about normal.
Hot wiring a 2004 Ram is almost impossible. If you to prevent the truck from starting, just remove the battery.
The core is probably plugged.
check your thermostat. or maybe your radiator is plugged up.
Just connect it to one of the brake lights hot lead, and ground it to the truck.
This frequently happens when the heater coil is going bad.
That can happen if they are low on freon.
heater core is more than likely leaking..
You probably could A) replace the gauge or B) take it to a dealership and have them look at it