As Tom mentioned what type of hydronic system you have,aqua-hot,oasis,etc.how many heat zones do you have in your coach?,your heat has zone pumps that circulate the heated solution to the radiators in the coach,each zone has its own pump,and one for engine heat if you have that option.Now there should be a main fuse panel by your unit or attached to it that has minnie fuses accompanied with little led lights the will let you know if the fuse is blown,maybe just a tired fuse which is an easy fix if it keeps blowing the fuse it’s your zone pump.I have an oasis system that replaced the aqua-hot,the zone pumps are $300.00+,don’t try using a cheap 12v pump (I know tried going that route they don’t hold up to the hot water). Now I don’t know where your unit is located but on my 2003 HR Imperial.I had to access it from my basement,the distribution center that houses the zone pumps is a separate box that’s separate from main heating unit.Look around on your heating unit to see if there is a toll free number to call,I know Oasis has one and they will walk you through any problem,yes you get to talk to a real tech and they are very patient and it’s as though they are looking over shoulder.Hey lots of luck ,getting to know just some of the workings of your motor home,it’s an unending learning process.Hope this gives you somewhere to start.