hey there. just got a beater se-r here in minnesota, and the temp guage is barely working. if i let the car sit and warm up, the guage goes up to 2/5 of the way, but once i start driving it drops to 0. i replaced the thermostat, but it did nothing. i was told elsewhere that it was a "sending unit", but i do not know exactly which one it is, or where it is located in the engine bay. can someone gimme a hand here?