Originally Posted by Jubal
Actually cold air is denser than warm air. The loop trap in the condensation drain line or water in the collection cup limits the loss of cold air out of the refer box.
No necessarily. Depends on air flow back there at 65 MPH. Who knows what it happening and I'm not going back there to see.
Our temperature does not rise without water in the cup unless we are driving.
I have played with it for 3 years now and on ours the temperature will raise within the first 20 miles without water in the cup. I have forgot to add water a few times and the temperature would start rising and as soon as I pulled over and added water the temperature would start dropping again. If you don't have problems with the temp rising while driving then don't bother with it. If you do it's a cheap, simple thing to try.