Double-flashing red LED indicates an open pressure switch; replaced pressure switch, but double-flashing LED remained. That has always fixed the problem in the past (about 1X per year, but 3X in past 6 months!) I figured it must be caused by something else; suspected the 50-60 yr old thermostat. Removed it and replaced it w/a new programmable Honeywell RTH2300 series thermostat. Simple installation, but still have the double-flashing red LED error. When I switch on the thermostat to HEAT, I hear the furnace go into its initial phase, but no burner lights, so the blower won't come on. Open to suggestions, as I've taken it as far as my limited knowledge is able, and it's going to be below freezing again this wknd! Thanks in advance for any ideas to help this along.