Originally Posted by racer_rr
Change the regulator. My old furnace started be difficult to light when cold or +8000ft. I replaced (maybe with a higher elevation version....don't remember) and all was well. Old reg was full of black hydrocarbon gunk.
My regulator was full of a tan colored, foul smelling, waxy substance that clogged it up and caused it to fail. The new regulator works well, but after a short time I experienced the same yellow flame when I run both stove burners. Using just one doesn't cause this, possibly due to less gas demand. Yellow indicates incomplete combustion and I suspect there is still some of the tan gunk getting through, but it's been this way for a year with no further issues. Since the combustion chamber for the furnace is a sealed unit, any byproduct of incomplete combustion (carbon monoxide)will simply be expelled out the exterior vent. You can replace the regulator with the tank full since it's down stream of the shutoff valve.