Howdy all, I just bought this truck and Im new to the Dodge world also....
I really like the truck so far, but the temp guage has me scratching my head. while driving down the road the temp guagesets at about 190 to 195, but when I stop it soars up to about 240 to 250.
I felt the top of the radiator hose/cap and it doesn't feel that hot.
could the change in voltage/amps from driving to idle be causing this change in the guage??? also, if I sit with the ignition in the accessory position and watch the guage, It will drop back down to normal 190 to 195 in about 3 minutes.

Its raining now, Ill post some pics in my sig tomorrow after the rain moves on.

 

3 possible things.1 fan is not working and while driving the air flow is cooling down engine.
2 thermostat is messed up.
3 radiator and system might need a good flushing

 

I just had the same problem with my 2000 Dodge Stratus. The temperature gauge would only move one notch and no further. I removed the thermostat which is located right under the radiator cap and easily accessible by removing two bolts. Upon removing it I saw that the coil was snapped and beyond salvaging. I went to the dealer and bought a new thermostat for 16 bucks and took about twenty minutes installing it and driving around to make sure there were no leaks. As long as you put the new one back exactly in the same position you took the old one out you should be fine. Now my gauge stays just under halfway and no higher and glad to say no leaks either. I am willing to bet this is what is wrong with your thermostat. Of course now I have to work on my heating system because for some reason I have no heat. Oh well....hope that helps.

 

sounds like your thermostat isnt opening all the way. this would allow your engine to still stay cool when your moving because the coolant is much cooler from the air passing through the radiator. then when your sitting still the radiator cant cool the coolant down as well and not enough is passing through to cool off your engine. i would definetly replace the thermostat before anything they are about 10-20 bucks. however it could also be your fan make sure its running when your engine is idleing. and if it is then its got to be your thermostat

 

Somethimg to add to this is how many miles on your rig? If it has high miles and the coolant has never been flushed, ther is probably a lot of debris built up in the coolant passages and radiator. That can be very dangerous if its not cleaned out and can cause some expensive repairs.