hi....yes the model number is on a tag, inside the furnace, you have to remove the rear panel from the casing to get to it, bit of a pain, but shouldnt be required just yet...now when it starts blowing cold air, i assume it eventually shuts down, should be about 3 minutes and then will shut down, since it doesnt detect a flame... is it shutting down?i will assume it is and go from there, save some back and forth with questions...most likely it is the gas valve is bad. it is trying to run, but the valve is not opening, hence not letting LP through, and after 3 minutes of running, it will give up....other possible problems are, thermocouple is bad... dirty or blocked burner....bad control board, although i doubt that.... or for some reason, no LP is reaching thr furnace.. i have seen a couple of cases where the LP line has become pinched or kinked, thus blocking the flow.. but usually this is in new trailers or after work has been done on the trailer.. but dont rule it out.. visually inspect the LP line as far as you can to make sure...to determin where the fault is, will need a bit more information though.... first... when you first turn it on.. do you hear it clicking, trying to light... should be a period of rapid clicking.. it will usually try 3 times before giving up... next, does it shut itself down after about 3 minutes?then...does the air flow comming out the outside vent, seem strong? there is a sail switch inside.. if for some reason, the fan cant spin fast enough, it will cause it not to light, for safety... some common simple reasons for this are voltage... needs to have a good voltage, at least 11.5volts, to operate correctly... do you have it plugged up to shore power when trying? make sure batteries are charged good and your seeing at least 12v at the battery..LP pressure is also important, needs 11.5" of water column to operate... low pressure wont really prevent the stove etc working, although can cause issues with water heaters.. unfortunately, not something you can check yourself as requires specialist measuring equipment and best done by a shop...unfortuntely, to check burners and gas valves etc, the furnace needs to be removed from the RV since all the components are internal... this is best done at a shop, who can test it properly and bench test the furnace correctly. if ou want to remove it yourself you can but unles you are confident in your skills with LP systems and so forth, i wouldnt attempt it....let me know answers to those questions and we can go from there....
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RVIA Certification
5 years RV repair and reconstruction, Fleetwood RV Training course completion.