Contrary to the instructions in my Marathon owners manual, Marathon Service and Engineering advised me that their 2006 coaches required the webasto unit to be operational to use either 12v coach heat or heat the Hot Water tanks when traveling - a capability my previous 2 Marathons had. After my Marathon warranty expired, I contacted Parliament's service dept.(Rick May) who assured me it would not be a problem to address my request. By adding several valves and related water lines, my 2006 coach now functions like my previous coaches and works like the Marathon owners manual reads. Work was accomplished in a day. This change eliminated the need to burn extra fuel to provide heat and hot water while traveling.Parliament has excellant service personnel who are very familiar with Marathon coaches.