I hope were not muddying the water too much, I believe OP gained a resolve and we do not confuse by added discussion, however some comments were made that IMO should not stand without clarification or rebuttal.
No RV furnace I'm aware of burners light & run with fan off. Either enlightenment, because all I know is how much I don't know, and there may be some RV furnace that operates as Rollin described. If there is such a heater I would like to know about it. If there is not, the information needs to be countered. If it is misunderstanding of how RV furnace works then someone else might learn something. Otherwise ...
I'm seeing down the road, someone noting that their fan no longer runs while burner is on or cycles on/off WHILE burner remains lit and generating heat (though redundant safety features should not allow that). Looking for information stumbles across this thread- reads the comments that the fan cycles on & off while burner is heating box-so assumes they don't have a problem.
Im not as tactful as mkirsch, but hope the OP and anyone else with similar issue reading this thread understands why its drifted from the original post and resolve (we hope) & doesnt detract.