Spiders love to spin web's in propane orifices and burners. If you have an air compressor turn off the heater and blow the propane orifice and air tube and burner areas off with high pressure air. I have to do this to mine occasionally and sometimes right after a very hard rain.
2006 GMC 2500HD CCSB 4x4 Duramax/Allison, Titan 52 gallon fuel tank, Prodigy Controller, B&W Companion Hitch
2010 Jayco Designer 35RLTS, Cummins/Onan RV QG 5500 EVAP, Progressive Industries EMS-PT50C, TST Systems 507 TPMS, RV Flex Armor Roof