I have a Carrier Model # 58RAV50-13112 Gas Furnace (fueled by propane) that isnít working properly. Itís a holiday weekend and Iím without heat, so any help would be greatly appreciated. The furnace was operating properly throughout last winter. However, now itĎs not working. The fan runs but only blows cold air. The system tries to start itself several times (and I can see a flame kick on each time), but after failing about three times to fully light up , it quits trying. (a safety ďlock outĒ I assume.) My propane tank is full and the incoming gas pressure is correct. The filter is new and the system is eleven years old. Replacing the Flame Sensor didnít help. What next? Replace the gas valve? No? Something else?