in the early 80's we where told in motor vehicle repair to test all thermostats in hot water before you put them in. you really can't do that anymore but it tells you they can be bad out of the box.

 

If your top hose is hot and the bottom hose is cold, your radiator is doing its job...if you still have a clutch driven fan (not electric conversion) your fan clutch may be engaged all the time drawing too much air through the rad causing the super cooling. If you have the time, and you have ruled out the temp switch, take the fan assy off (assuming the wp pulley is pressed on) and let the truck idle while watching the temp gauge and paying attention to the temp of the rad hoses. You should see an increase of engine temp within just a few minutes. if so, replace your fan clutch or convert to electric fan with adjustable thermostat (increase in power is noticeable on 5.2 trucks).

 

One more thought...the parts stores are probably gonna refer to the sensor for the gauge as the temperature "switch" the sensor for the ECU is normally called the temperature sensor. This should help when you call the parts store.

 

As always, thanks so much for the continued help from everyone. The Dakota is now 5 hours away with my son at college so I am going to have to forgoe any further testing but everythning that I have done so far has been a step in the right direction and I appreciate everyone's help.