We recently bought a doublewide that has an Intertherm furnace for heat. I think the model is E2EB-015HA. It seems the furnace won't stay warm.

If we turn the unit off and then flip both the two breakers that are beneith the blower off, and then back on, the air gets warm again and will stay warm for maybe a day or two and be fine.. Over a period however, the air coming out gets cold again and it will just run and run and won't get warm. Obviously we have a problem despite my stubborn SO's insistence that this is just how older trailer heat is *rolley eyes* Any suggestions?