If the flame is not burning BLUE it will soot up on you big time. You may have to clean the flu and other areas around the burner to get the BLUE FLAME back.
It could also be not enough oxygen around the heater to work properly... The trick is to always see a BLUE FLAME...
How does the propane flame look when using the stove top burners. same thing there - should be a good BLUE FLAME...
Do a GOOGLE SEARCH with the same question... Lots of info there...
Roy Ken
My Posts are IMHO based on my experiences - Words in CAPS does not mean I am shouting
Roy - Carolyn
RETIRED DOAF/DON/DOD/CONTR RADIO TECH (42yrs)
K9PHT (Since 1957) 146.52M
2010 F150, 5.4,3:73 Gears,SCab
2008 Starcraft 14RT EU2000i GEN
2005 Flagstaff 8528RESS