Just one more thing to think about. Recently on a trip to Colorado with my elderly uncle on board, I had just replaced the system heat unit in the water/sewer bay. It had failed and would not put out any heat.The outside temp was about 15 degrees and I wanted to make sure I had wired and installed the unit correctly. I bought a remote temp sensor and mounted it the the water bay, and put the receiver by the front dash where I could see it. It worked great and the temp would stay between 38 and 40 degrees.
I had been watching the temp and the next thing I saw was the temp at 31 degrees and dropping. I really thought since I had just replaced it, It had to be a wiring problem. I had my wife check the switch on the control panel and it had been turned off. The problem started when my Uncle went back to use the bathroom. He is unsteady on his feet and even though I had pulled into a rest stop, he had turned the heat off when he used his hands along the wall to support himself.
For about 10 bucks it is worth getting a remote temp sensor to put in the water service bay if you are traveling in cold weather. To avoid the problem again on the trip, I taped a water bottle lid over the switch to keep it from accidentally being turned off. No way of knowing the heat is not working from the driver seat w/o the remote sensor. Cheap insurance to prevent a big problem.
Cal Kazebeer F398498