Barlow46

Dean, Not to be insulting, but did you make sure you replaced 12V batteries and not 6v batteries. I know many people who use two 6v batteries in their fifth wheels rather than one 12V battery. Here is a link that explains it easier than I can. You probably already have it wired correctly but just want to throw out another possible option.http://www.solarrvpanels.com/index.php/tag/wiring-6-volt-batteries-in-series/

Be sure to read what Gary Spires has written on the subject. His background is in diesel filtration systems. Here is a link that will give you more information before you change the filter. My link