I have a theme model RGRT-07EMAES gas furnace and since it is extremely cold like zero degrees outside the furnace will run for a little bit and stop. If I turn power off and turn it back on to furnace it will start up again and shut off to soon. If I leave inspection cover off for burner area it will continue to run with no problem. Fresh air intake had some snow blocking intake and I cleared the snow and it seamed to run longer but then shut off again. Help me please. Very cold and frustrated! Roy