Hi, we are new at RV'ing and bought an older 1989 Windcruiser. We ran out of propane day before yesterday so the water heater went out. We got propane then tried relighting the water heater and it won't stay lit. I have cleaned soot and mud dobbers out as far as I can reach inside but don't want to damage anything. I can't reach all the way to the burners. Can someone guide me as to how to clean them out? Thanks!