We have been having problems with the heat distribution in our 1998 Southwind 32V. Soon after starting the heat on a chilly morning, it would about drive you out of the bedroom, but the bathroom had just about no heat and the front of the coach was not getting enough, compared to the bedroom. The front thermostat is the one that the furnace uses.
I had a little session a couple of days ago, and have made some improvements to the situation (though likely not a complete cure). Here's what I found and what I did about it:
There is a small duct that runs to the bathroom (a small space). The plate where this duct connects to the furnace was partially unhooked, allowing air to escape instead of being pushed through the duct. I corrected this problem. I also found that the duct was laying across the top of the 12V power converter. I used a large cable tie to support it such that there is clearance around the power converter. The round bathroom register vent has an air control knob in the center. On close inspection, I discovered that this thing works bass-ackwards. Clockwise opens the vent and counter-clockwise closes it! I thought I had the thing full open and it was really closed.
Now that I know how it works, I might have better luck getting heat in the bathroom.
The bedroom has two ducts and two round vents, which do not have the flow control knob. I took these vents apart and put a strip of duct tape across each one of them, on the end that inserts into the duct. This way, I have a little less than half the cross-sectional area opening into the bedroom. This should force a greater portion of the air out the two vents in the front of the coach.
I tried the furnace a bit after I made these mods, but it wasn't in chilly conditions. This weekend, I hope to give it more of a test. My guess is that the heat distribution may still not be ideal for my taste, but should be better.