Hello everyone, new guy here needing advice. My temp gauge on my 2001 Ram (3.9L) will only show engine temp at idle. Once going down the road, the needle bottoms out until the next time I come to a stop. I've already replaced the temp sensor twice. Also, on cold mornings, I noticed that when the needle drops out, the heater air cools off some too. Ideas? Anybody ever heard of this before? Is there maybe another sensor that I'm missing and don't know about? The parts guy at my local Dodge parts counter said that there is only one sensor for engine temp. I'm all out of guesses!