I moved in to a 1988 holiday rambler 24' about 5 months ago, to live In full time. And until recently, the furnace was running perfectly and didn't have any issues. within the past couple days, after the startup cycle for the furnace has completed and it's putting out decent heat, about 20 minutes or so in to the cycle, the fan slows way down, and just seems to put itself in to limp mode. After a few minutes of it, I can smell burnt propane fumes. So I turn it off for safety reasons. I do have it connected to approximately 200' extension cord in to a regular house. (No other choice) I do know the heater is a hydroflame. Other than that, I can't find a model #. Any help would be extremely helpful and much appreciated. I will be fixing it myself as I can't afford someone to look at it for me.