Jimmy, here is the link to my Owners Manual that describes the operation of the Primus system
http://tinyurl.com/38qo4m
The section on the Primus system begins on page 34 of the manual, marked Page 11.1 - 11.4.
The manual indicates that there are two independent loops for the Primus. Loop one just serves the front of the coach. This is obviously the loop that is not working on your coach. The secondary loop heats the rear half of the coach, the water heater and main engine heating.
Look at Dupree Product's site
http://www.dupreeproducts.com/SearchResults.asp?Cat=27 for a drawing of the components of the Primus system. Steve Birtles sells several of the parts to maintain the system. He is a regular on the Blue Bird Wanderlodge forums.
The Primus systems required maintenance but they were good systems. They have been replaced by Aqua-Hot in more recent coaches.
Hope this helps.