Since your coach is of the same era as mine it may have a Hurricane heater. If so you're in luck. Here's a link to some videos on the ITR (Hurricane) website.
ITR - Hurricane Videos
If the coach is new to you or used infrequently, it's easy to overlook the requirement for turning on the fan switches on the panels in the cockpit and bedroom. Just setting the thermostat to "Furnace" for the desired zones is not enough. The fans have to be enabled, though the thermostat via the Hurricane control module actually turns them on and off.
On edit - our posts crossed in the mail. I see you do in fact have a Hurricane. Watch the video on troubleshooting. It really gets you going in the right direction.