Hello, I have a frigidaire gas heating furnace model fg6rc100c-16 problem with no heat. The furnace appears to stay on constantly blowing cold air when the thermostat is turned off. I had to remove the lower furnace panel in order for the unit to shut down, there was a pin switch that activates the furnace. I noticed on the circuit board that flashed 1 red light every few seconds indicating a problem. There was a trouble shoot chart on the panel indicating "limit circuit open or external load on (w)". What does that mean and how can I fix this? Thanks

Your problem sounds like a air flow issue dirty filter,blocked vents, blower not working,A coil blocked something is causing the unit to overheat and go off on limit..